root/net/ipv4/tcp.c

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DEFINITIONS

This source file includes following definitions.
  1. tcp_find_established
  2. tcp_close_pending
  3. tcp_time_wait
  4. tcp_err
  5. tcp_readable
  6. tcp_listen_select
  7. tcp_select
  8. tcp_ioctl
  9. tcp_send_check
  10. tcp_build_header
  11. wait_for_tcp_connect
  12. wait_for_tcp_memory
  13. do_tcp_sendmsg
  14. tcp_sendmsg
  15. tcp_read_wakeup
  16. tcp_recv_urg
  17. tcp_eat_skb
  18. cleanup_rbuf
  19. tcp_recvmsg
  20. tcp_close_state
  21. tcp_shutdown
  22. closing
  23. tcp_close
  24. wait_for_connect
  25. tcp_accept
  26. tcp_connect
  27. tcp_setsockopt
  28. tcp_getsockopt

   1 /*
   2  * INET         An implementation of the TCP/IP protocol suite for the LINUX
   3  *              operating system.  INET is implemented using the  BSD Socket
   4  *              interface as the means of communication with the user level.
   5  *
   6  *              Implementation of the Transmission Control Protocol(TCP).
   7  *
   8  * Version:     @(#)tcp.c       1.0.16  05/25/93
   9  *
  10  * Authors:     Ross Biro, <bir7@leland.Stanford.Edu>
  11  *              Fred N. van Kempen, <waltje@uWalt.NL.Mugnet.ORG>
  12  *              Mark Evans, <evansmp@uhura.aston.ac.uk>
  13  *              Corey Minyard <wf-rch!minyard@relay.EU.net>
  14  *              Florian La Roche, <flla@stud.uni-sb.de>
  15  *              Charles Hedrick, <hedrick@klinzhai.rutgers.edu>
  16  *              Linus Torvalds, <torvalds@cs.helsinki.fi>
  17  *              Alan Cox, <gw4pts@gw4pts.ampr.org>
  18  *              Matthew Dillon, <dillon@apollo.west.oic.com>
  19  *              Arnt Gulbrandsen, <agulbra@nvg.unit.no>
  20  *              Jorge Cwik, <jorge@laser.satlink.net>
  21  *
  22  * Fixes:
  23  *              Alan Cox        :       Numerous verify_area() calls
  24  *              Alan Cox        :       Set the ACK bit on a reset
  25  *              Alan Cox        :       Stopped it crashing if it closed while
  26  *                                      sk->inuse=1 and was trying to connect
  27  *                                      (tcp_err()).
  28  *              Alan Cox        :       All icmp error handling was broken
  29  *                                      pointers passed where wrong and the
  30  *                                      socket was looked up backwards. Nobody
  31  *                                      tested any icmp error code obviously.
  32  *              Alan Cox        :       tcp_err() now handled properly. It
  33  *                                      wakes people on errors. select
  34  *                                      behaves and the icmp error race
  35  *                                      has gone by moving it into sock.c
  36  *              Alan Cox        :       tcp_send_reset() fixed to work for
  37  *                                      everything not just packets for
  38  *                                      unknown sockets.
  39  *              Alan Cox        :       tcp option processing.
  40  *              Alan Cox        :       Reset tweaked (still not 100%) [Had
  41  *                                      syn rule wrong]
  42  *              Herp Rosmanith  :       More reset fixes
  43  *              Alan Cox        :       No longer acks invalid rst frames.
  44  *                                      Acking any kind of RST is right out.
  45  *              Alan Cox        :       Sets an ignore me flag on an rst
  46  *                                      receive otherwise odd bits of prattle
  47  *                                      escape still
  48  *              Alan Cox        :       Fixed another acking RST frame bug.
  49  *                                      Should stop LAN workplace lockups.
  50  *              Alan Cox        :       Some tidyups using the new skb list
  51  *                                      facilities
  52  *              Alan Cox        :       sk->keepopen now seems to work
  53  *              Alan Cox        :       Pulls options out correctly on accepts
  54  *              Alan Cox        :       Fixed assorted sk->rqueue->next errors
  55  *              Alan Cox        :       PSH doesn't end a TCP read. Switched a
  56  *                                      bit to skb ops.
  57  *              Alan Cox        :       Tidied tcp_data to avoid a potential
  58  *                                      nasty.
  59  *              Alan Cox        :       Added some better commenting, as the
  60  *                                      tcp is hard to follow
  61  *              Alan Cox        :       Removed incorrect check for 20 * psh
  62  *      Michael O'Reilly        :       ack < copied bug fix.
  63  *      Johannes Stille         :       Misc tcp fixes (not all in yet).
  64  *              Alan Cox        :       FIN with no memory -> CRASH
  65  *              Alan Cox        :       Added socket option proto entries.
  66  *                                      Also added awareness of them to accept.
  67  *              Alan Cox        :       Added TCP options (SOL_TCP)
  68  *              Alan Cox        :       Switched wakeup calls to callbacks,
  69  *                                      so the kernel can layer network
  70  *                                      sockets.
  71  *              Alan Cox        :       Use ip_tos/ip_ttl settings.
  72  *              Alan Cox        :       Handle FIN (more) properly (we hope).
  73  *              Alan Cox        :       RST frames sent on unsynchronised
  74  *                                      state ack error.
  75  *              Alan Cox        :       Put in missing check for SYN bit.
  76  *              Alan Cox        :       Added tcp_select_window() aka NET2E
  77  *                                      window non shrink trick.
  78  *              Alan Cox        :       Added a couple of small NET2E timer
  79  *                                      fixes
  80  *              Charles Hedrick :       TCP fixes
  81  *              Toomas Tamm     :       TCP window fixes
  82  *              Alan Cox        :       Small URG fix to rlogin ^C ack fight
  83  *              Charles Hedrick :       Rewrote most of it to actually work
  84  *              Linus           :       Rewrote tcp_read() and URG handling
  85  *                                      completely
  86  *              Gerhard Koerting:       Fixed some missing timer handling
  87  *              Matthew Dillon  :       Reworked TCP machine states as per RFC
  88  *              Gerhard Koerting:       PC/TCP workarounds
  89  *              Adam Caldwell   :       Assorted timer/timing errors
  90  *              Matthew Dillon  :       Fixed another RST bug
  91  *              Alan Cox        :       Move to kernel side addressing changes.
  92  *              Alan Cox        :       Beginning work on TCP fastpathing
  93  *                                      (not yet usable)
  94  *              Arnt Gulbrandsen:       Turbocharged tcp_check() routine.
  95  *              Alan Cox        :       TCP fast path debugging
  96  *              Alan Cox        :       Window clamping
  97  *              Michael Riepe   :       Bug in tcp_check()
  98  *              Matt Dillon     :       More TCP improvements and RST bug fixes
  99  *              Matt Dillon     :       Yet more small nasties remove from the
 100  *                                      TCP code (Be very nice to this man if
 101  *                                      tcp finally works 100%) 8)
 102  *              Alan Cox        :       BSD accept semantics.
 103  *              Alan Cox        :       Reset on closedown bug.
 104  *      Peter De Schrijver      :       ENOTCONN check missing in tcp_sendto().
 105  *              Michael Pall    :       Handle select() after URG properly in
 106  *                                      all cases.
 107  *              Michael Pall    :       Undo the last fix in tcp_read_urg()
 108  *                                      (multi URG PUSH broke rlogin).
 109  *              Michael Pall    :       Fix the multi URG PUSH problem in
 110  *                                      tcp_readable(), select() after URG
 111  *                                      works now.
 112  *              Michael Pall    :       recv(...,MSG_OOB) never blocks in the
 113  *                                      BSD api.
 114  *              Alan Cox        :       Changed the semantics of sk->socket to
 115  *                                      fix a race and a signal problem with
 116  *                                      accept() and async I/O.
 117  *              Alan Cox        :       Relaxed the rules on tcp_sendto().
 118  *              Yury Shevchuk   :       Really fixed accept() blocking problem.
 119  *              Craig I. Hagan  :       Allow for BSD compatible TIME_WAIT for
 120  *                                      clients/servers which listen in on
 121  *                                      fixed ports.
 122  *              Alan Cox        :       Cleaned the above up and shrank it to
 123  *                                      a sensible code size.
 124  *              Alan Cox        :       Self connect lockup fix.
 125  *              Alan Cox        :       No connect to multicast.
 126  *              Ross Biro       :       Close unaccepted children on master
 127  *                                      socket close.
 128  *              Alan Cox        :       Reset tracing code.
 129  *              Alan Cox        :       Spurious resets on shutdown.
 130  *              Alan Cox        :       Giant 15 minute/60 second timer error
 131  *              Alan Cox        :       Small whoops in selecting before an
 132  *                                      accept.
 133  *              Alan Cox        :       Kept the state trace facility since
 134  *                                      it's handy for debugging.
 135  *              Alan Cox        :       More reset handler fixes.
 136  *              Alan Cox        :       Started rewriting the code based on
 137  *                                      the RFC's for other useful protocol
 138  *                                      references see: Comer, KA9Q NOS, and
 139  *                                      for a reference on the difference
 140  *                                      between specifications and how BSD
 141  *                                      works see the 4.4lite source.
 142  *              A.N.Kuznetsov   :       Don't time wait on completion of tidy
 143  *                                      close.
 144  *              Linus Torvalds  :       Fin/Shutdown & copied_seq changes.
 145  *              Linus Torvalds  :       Fixed BSD port reuse to work first syn
 146  *              Alan Cox        :       Reimplemented timers as per the RFC
 147  *                                      and using multiple timers for sanity.
 148  *              Alan Cox        :       Small bug fixes, and a lot of new
 149  *                                      comments.
 150  *              Alan Cox        :       Fixed dual reader crash by locking
 151  *                                      the buffers (much like datagram.c)
 152  *              Alan Cox        :       Fixed stuck sockets in probe. A probe
 153  *                                      now gets fed up of retrying without
 154  *                                      (even a no space) answer.
 155  *              Alan Cox        :       Extracted closing code better
 156  *              Alan Cox        :       Fixed the closing state machine to
 157  *                                      resemble the RFC.
 158  *              Alan Cox        :       More 'per spec' fixes.
 159  *              Jorge Cwik      :       Even faster checksumming.
 160  *              Alan Cox        :       tcp_data() doesn't ack illegal PSH
 161  *                                      only frames. At least one pc tcp stack
 162  *                                      generates them.
 163  *              Alan Cox        :       Cache last socket.
 164  *              Alan Cox        :       Per route irtt.
 165  *              Matt Day        :       Select() match BSD precisely on error
 166  *              Alan Cox        :       New buffers
 167  *              Marc Tamsky     :       Various sk->prot->retransmits and
 168  *                                      sk->retransmits misupdating fixed.
 169  *                                      Fixed tcp_write_timeout: stuck close,
 170  *                                      and TCP syn retries gets used now.
 171  *              Mark Yarvis     :       In tcp_read_wakeup(), don't send an
 172  *                                      ack if stat is TCP_CLOSED.
 173  *              Alan Cox        :       Look up device on a retransmit - routes may
 174  *                                      change. Doesn't yet cope with MSS shrink right
 175  *                                      but its a start!
 176  *              Marc Tamsky     :       Closing in closing fixes.
 177  *              Mike Shaver     :       RFC1122 verifications.
 178  *              Alan Cox        :       rcv_saddr errors.
 179  *              Alan Cox        :       Block double connect().
 180  *              Alan Cox        :       Small hooks for enSKIP.
 181  *              Alexey Kuznetsov:       Path MTU discovery.
 182  *              Alan Cox        :       Support soft errors.
 183  *              Alan Cox        :       Fix MTU discovery pathological case
 184  *                                      when the remote claims no mtu!
 185  *              Marc Tamsky     :       TCP_CLOSE fix.
 186  *              Colin (G3TNE)   :       Send a reset on syn ack replies in
 187  *                                      window but wrong (fixes NT lpd problems)
 188  *              Pedro Roque     :       Better TCP window handling, delayed ack.
 189  *              Joerg Reuter    :       No modification of locked buffers in
 190  *                                      tcp_do_retransmit()
 191  *              Eric Schenk     :       Changed receiver side silly window
 192  *                                      avoidance algorithm to BSD style
 193  *                                      algorithm. This doubles throughput
 194  *                                      against machines running Solaris,
 195  *                                      and seems to result in general
 196  *                                      improvement.
 197  *              Eric Schenk     :       Changed receiver side silly window
 198  *                                      avoidance algorithm to BSD style
 199  *                                      algorithm. This doubles throughput
 200  *                                      against machines running Solaris,
 201  *                                      and seems to result in general
 202  *                                      improvement.
 203  *
 204  * To Fix:
 205  *              Fast path the code. Two things here - fix the window calculation
 206  *              so it doesn't iterate over the queue, also spot packets with no funny
 207  *              options arriving in order and process directly.
 208  *
 209  *              Rewrite output state machine to use a single queue.
 210  *              Speed up input assembly algorithm.
 211  *              RFC1323 - PAWS and window scaling. PAWS is required for IPv6 so we
 212  *              could do with it working on IPv4
 213  *              User settable/learned rtt/max window/mtu
 214  *
 215  *              Change the fundamental structure to a single send queue maintained
 216  *              by TCP (removing the bogus ip stuff [thus fixing mtu drops on
 217  *              active routes too]). Cut the queue off in tcp_retransmit/
 218  *              tcp_transmit.
 219  *              Change the receive queue to assemble as it goes. This lets us
 220  *              dispose of most of tcp_sequence, half of tcp_ack and chunks of
 221  *              tcp_data/tcp_read as well as the window shrink crud.
 222  *              Separate out duplicated code - tcp_alloc_skb, tcp_build_ack
 223  *              tcp_queue_skb seem obvious routines to extract.
 224  *
 225  *              This program is free software; you can redistribute it and/or
 226  *              modify it under the terms of the GNU General Public License
 227  *              as published by the Free Software Foundation; either version
 228  *              2 of the License, or(at your option) any later version.
 229  *
 230  * Description of States:
 231  *
 232  *      TCP_SYN_SENT            sent a connection request, waiting for ack
 233  *
 234  *      TCP_SYN_RECV            received a connection request, sent ack,
 235  *                              waiting for final ack in three-way handshake.
 236  *
 237  *      TCP_ESTABLISHED         connection established
 238  *
 239  *      TCP_FIN_WAIT1           our side has shutdown, waiting to complete
 240  *                              transmission of remaining buffered data
 241  *
 242  *      TCP_FIN_WAIT2           all buffered data sent, waiting for remote
 243  *                              to shutdown
 244  *
 245  *      TCP_CLOSING             both sides have shutdown but we still have
 246  *                              data we have to finish sending
 247  *
 248  *      TCP_TIME_WAIT           timeout to catch resent junk before entering
 249  *                              closed, can only be entered from FIN_WAIT2
 250  *                              or CLOSING.  Required because the other end
 251  *                              may not have gotten our last ACK causing it
 252  *                              to retransmit the data packet (which we ignore)
 253  *
 254  *      TCP_CLOSE_WAIT          remote side has shutdown and is waiting for
 255  *                              us to finish writing our data and to shutdown
 256  *                              (we have to close() to move on to LAST_ACK)
 257  *
 258  *      TCP_LAST_ACK            out side has shutdown after remote has
 259  *                              shutdown.  There may still be data in our
 260  *                              buffer that we have to finish sending
 261  *
 262  *      TCP_CLOSE               socket is finished
 263  */
 264 
 265 /*
 266  * RFC1122 status:
 267  * NOTE: I'm not going to be doing comments in the code for this one except
 268  * for violations and the like.  tcp.c is just too big... If I say something
 269  * "does?" or "doesn't?", it means I'm not sure, and will have to hash it out
 270  * with Alan. -- MS 950903
 271  *
 272  * Use of PSH (4.2.2.2)
 273  *   MAY aggregate data sent without the PSH flag. (does)
 274  *   MAY queue data received without the PSH flag. (does)
 275  *   SHOULD collapse successive PSH flags when it packetizes data. (doesn't)
 276  *   MAY implement PSH on send calls. (doesn't, thus:)
 277  *     MUST NOT buffer data indefinitely (doesn't [1 second])
 278  *     MUST set PSH on last segment (does)
 279  *   MAY pass received PSH to application layer (doesn't)
 280  *   SHOULD send maximum-sized segment whenever possible. (almost always does)
 281  *
 282  * Window Size (4.2.2.3, 4.2.2.16)
 283  *   MUST treat window size as an unsigned number (does)
 284  *   SHOULD treat window size as a 32-bit number (does not)
 285  *   MUST NOT shrink window once it is offered (does not normally)
 286  *
 287  * Urgent Pointer (4.2.2.4)
 288  * **MUST point urgent pointer to last byte of urgent data (not right
 289  *     after). (doesn't, to be like BSD)
 290  *   MUST inform application layer asynchronously of incoming urgent
 291  *     data. (does)
 292  *   MUST provide application with means of determining the amount of
 293  *     urgent data pending. (does)
 294  * **MUST support urgent data sequence of arbitrary length. (doesn't, but
 295  *   it's sort of tricky to fix, as urg_ptr is a 16-bit quantity)
 296  *      [Follows BSD 1 byte of urgent data]
 297  *
 298  * TCP Options (4.2.2.5)
 299  *   MUST be able to receive TCP options in any segment. (does)
 300  *   MUST ignore unsupported options (does)
 301  *
 302  * Maximum Segment Size Option (4.2.2.6)
 303  *   MUST implement both sending and receiving MSS. (does)
 304  *   SHOULD send an MSS with every SYN where receive MSS != 536 (MAY send
 305  *     it always). (does, even when MSS == 536, which is legal)
 306  *   MUST assume MSS == 536 if no MSS received at connection setup (does)
 307  *   MUST calculate "effective send MSS" correctly:
 308  *     min(physical_MTU, remote_MSS+20) - sizeof(tcphdr) - sizeof(ipopts)
 309  *     (does - but allows operator override)
 310  *
 311  * TCP Checksum (4.2.2.7)
 312  *   MUST generate and check TCP checksum. (does)
 313  *
 314  * Initial Sequence Number Selection (4.2.2.8)
 315  *   MUST use the RFC 793 clock selection mechanism.  (doesn't, but it's
 316  *     OK: RFC 793 specifies a 250KHz clock, while we use 1MHz, which is
 317  *     necessary for 10Mbps networks - and harder than BSD to spoof!)
 318  *
 319  * Simultaneous Open Attempts (4.2.2.10)
 320  *   MUST support simultaneous open attempts (does)
 321  *
 322  * Recovery from Old Duplicate SYN (4.2.2.11)
 323  *   MUST keep track of active vs. passive open (does)
 324  *
 325  * RST segment (4.2.2.12)
 326  *   SHOULD allow an RST segment to contain data (does, but doesn't do
 327  *     anything with it, which is standard)
 328  *
 329  * Closing a Connection (4.2.2.13)
 330  *   MUST inform application of whether connection was closed by RST or
 331  *     normal close. (does)
 332  *   MAY allow "half-duplex" close (treat connection as closed for the
 333  *     local app, even before handshake is done). (does)
 334  *   MUST linger in TIME_WAIT for 2 * MSL (does)
 335  *
 336  * Retransmission Timeout (4.2.2.15)
 337  *   MUST implement Jacobson's slow start and congestion avoidance
 338  *     stuff. (does)
 339  *
 340  * Probing Zero Windows (4.2.2.17)
 341  *   MUST support probing of zero windows. (does)
 342  *   MAY keep offered window closed indefinitely. (does)
 343  *   MUST allow remote window to stay closed indefinitely. (does)
 344  *
 345  * Passive Open Calls (4.2.2.18)
 346  *   MUST NOT let new passive open affect other connections. (doesn't)
 347  *   MUST support passive opens (LISTENs) concurrently. (does)
 348  *
 349  * Time to Live (4.2.2.19)
 350  *   MUST make TCP TTL configurable. (does - IP_TTL option)
 351  *
 352  * Event Processing (4.2.2.20)
 353  *   SHOULD queue out-of-order segments. (does)
 354  *   MUST aggregate ACK segments whenever possible. (does but badly)
 355  *
 356  * Retransmission Timeout Calculation (4.2.3.1)
 357  *   MUST implement Karn's algorithm and Jacobson's algorithm for RTO
 358  *     calculation. (does, or at least explains them in the comments 8*b)
 359  *  SHOULD initialize RTO to 0 and RTT to 3. (does)
 360  *
 361  * When to Send an ACK Segment (4.2.3.2)
 362  *   SHOULD implement delayed ACK. (does)
 363  *   MUST keep ACK delay < 0.5 sec. (does)
 364  *
 365  * When to Send a Window Update (4.2.3.3)
 366  *   MUST implement receiver-side SWS. (does)
 367  *
 368  * When to Send Data (4.2.3.4)
 369  *   MUST implement sender-side SWS. (does)
 370  *   SHOULD implement Nagle algorithm. (does)
 371  *
 372  * TCP Connection Failures (4.2.3.5)
 373  *  MUST handle excessive retransmissions "properly" (see the RFC). (does)
 374  *   SHOULD inform application layer of soft errors. (does)
 375  *
 376  * TCP Keep-Alives (4.2.3.6)
 377  *   MAY provide keep-alives. (does)
 378  *   MUST make keep-alives configurable on a per-connection basis. (does)
 379  *   MUST default to no keep-alives. (does)
 380  * **MUST make keep-alive interval configurable. (doesn't)
 381  * **MUST make default keep-alive interval > 2 hours. (doesn't)
 382  *   MUST NOT interpret failure to ACK keep-alive packet as dead
 383  *     connection. (doesn't)
 384  *   SHOULD send keep-alive with no data. (does)
 385  *
 386  * TCP Multihoming (4.2.3.7)
 387  *   MUST get source address from IP layer before sending first
 388  *     SYN. (does)
 389  *   MUST use same local address for all segments of a connection. (does)
 390  *
 391  * IP Options (4.2.3.8)
 392  *   MUST ignore unsupported IP options. (does)
 393  *   MAY support Time Stamp and Record Route. (does)
 394  *   MUST allow application to specify a source route. (does)
 395  *   MUST allow received Source Route option to set route for all future
 396  *     segments on this connection. (does not (security issues))
 397  *
 398  * ICMP messages (4.2.3.9)
 399  *   MUST act on ICMP errors. (does)
 400  *   MUST slow transmission upon receipt of a Source Quench. (does)
 401  *   MUST NOT abort connection upon receipt of soft Destination
 402  *     Unreachables (0, 1, 5), Time Exceededs and Parameter
 403  *     Problems. (doesn't)
 404  *   SHOULD report soft Destination Unreachables etc. to the
 405  *     application. (does)
 406  *   SHOULD abort connection upon receipt of hard Destination Unreachable
 407  *     messages (2, 3, 4). (does)
 408  *
 409  * Remote Address Validation (4.2.3.10)
 410  *   MUST reject as an error OPEN for invalid remote IP address. (does)
 411  *   MUST ignore SYN with invalid source address. (does)
 412  *   MUST silently discard incoming SYN for broadcast/multicast
 413  *     address. (does)
 414  *
 415  * Asynchronous Reports (4.2.4.1)
 416  * MUST provide mechanism for reporting soft errors to application
 417  *     layer. (does)
 418  *
 419  * Type of Service (4.2.4.2)
 420  *   MUST allow application layer to set Type of Service. (does IP_TOS)
 421  *
 422  * (Whew. -- MS 950903)
 423  **/
 424 
 425 #include <linux/config.h>
 426 #include <linux/types.h>
 427 #include <linux/fcntl.h>
 428 
 429 #include <net/icmp.h>
 430 #include <net/tcp.h>
 431 
 432 #include <asm/segment.h>
 433 
 434 unsigned long seq_offset;
 435 struct tcp_mib  tcp_statistics;
 436 
 437 static void tcp_close(struct sock *sk, unsigned long timeout);
 438 
 439 /*
 440  *      Find someone to 'accept'. Must be called with
 441  *      the socket locked or with interrupts disabled
 442  */
 443 
 444 static struct sk_buff *tcp_find_established(struct sock *s)
     /* [previous][next][first][last][top][bottom][index][help] */
 445 {
 446         struct sk_buff *p=skb_peek(&s->receive_queue);
 447         if(p==NULL)
 448                 return NULL;
 449         do
 450         {
 451                 if(p->sk->state == TCP_ESTABLISHED || p->sk->state >= TCP_FIN_WAIT1)
 452                         return p;
 453                 p=p->next;
 454         }
 455         while(p!=(struct sk_buff *)&s->receive_queue);
 456         return NULL;
 457 }
 458 
 459 /*
 460  *      This routine closes sockets which have been at least partially
 461  *      opened, but not yet accepted. Currently it is only called by
 462  *      tcp_close, and timeout mirrors the value there.
 463  */
 464 
 465 static void tcp_close_pending (struct sock *sk)
     /* [previous][next][first][last][top][bottom][index][help] */
 466 {
 467         struct sk_buff *skb;
 468 
 469         while ((skb = skb_dequeue(&sk->receive_queue)) != NULL)
 470         {
 471                 tcp_close(skb->sk, 0);
 472                 kfree_skb(skb, FREE_READ);
 473         }
 474         return;
 475 }
 476 
 477 /*
 478  *      Enter the time wait state.
 479  */
 480 
 481 void tcp_time_wait(struct sock *sk)
     /* [previous][next][first][last][top][bottom][index][help] */
 482 {
 483         tcp_set_state(sk,TCP_TIME_WAIT);
 484         sk->shutdown = SHUTDOWN_MASK;
 485         if (!sk->dead)
 486                 sk->state_change(sk);
 487         tcp_reset_msl_timer(sk, TIME_CLOSE, TCP_TIMEWAIT_LEN);
 488 }
 489 
 490 
 491 /*
 492  * This routine is called by the ICMP module when it gets some
 493  * sort of error condition.  If err < 0 then the socket should
 494  * be closed and the error returned to the user.  If err > 0
 495  * it's just the icmp type << 8 | icmp code.  After adjustment
 496  * header points to the first 8 bytes of the tcp header.  We need
 497  * to find the appropriate port.
 498  */
 499 
 500 void tcp_err(int type, int code, unsigned char *header, __u32 daddr,
     /* [previous][next][first][last][top][bottom][index][help] */
 501         __u32 saddr, struct inet_protocol *protocol)
 502 {
 503         struct tcphdr *th = (struct tcphdr *)header;
 504         struct sock *sk;
 505 
 506         /*
 507          *      This one is _WRONG_. FIXME urgently.
 508          */
 509 #ifndef CONFIG_NO_PATH_MTU_DISCOVERY
 510         struct iphdr *iph=(struct iphdr *)(header-sizeof(struct iphdr));
 511 #endif
 512         th =(struct tcphdr *)header;
 513         sk = get_sock(&tcp_prot, th->source, daddr, th->dest, saddr);
 514 
 515         if (sk == NULL)
 516                 return;
 517 
 518         if (type == ICMP_SOURCE_QUENCH)
 519         {
 520                 /*
 521                  * FIXME:
 522                  * For now we will just trigger a linear backoff.
 523                  * The slow start code should cause a real backoff here.
 524                  */
 525                 if (sk->cong_window > 4)
 526                         sk->cong_window--;
 527                 return;
 528         }
 529 
 530         if (type == ICMP_PARAMETERPROB)
 531         {
 532                 sk->err=EPROTO;
 533                 sk->error_report(sk);
 534         }
 535 
 536 #ifndef CONFIG_NO_PATH_MTU_DISCOVERY
 537         if (type == ICMP_DEST_UNREACH && code == ICMP_FRAG_NEEDED)
 538         {
 539                 struct rtable * rt;
 540                 /*
 541                  * Ugly trick to pass MTU to protocol layer.
 542                  * Really we should add argument "info" to error handler.
 543                  */
 544                 unsigned short new_mtu = ntohs(iph->id);
 545 
 546                 if ((rt = sk->ip_route_cache) != NULL)
 547                         if (rt->rt_mtu > new_mtu)
 548                                 rt->rt_mtu = new_mtu;
 549 
 550                 if (sk->mtu > new_mtu - sizeof(struct iphdr) - sizeof(struct tcphdr)
 551                         && new_mtu > sizeof(struct iphdr)+sizeof(struct tcphdr))
 552                         sk->mtu = new_mtu - sizeof(struct iphdr) - sizeof(struct tcphdr);
 553 
 554                 return;
 555         }
 556 #endif
 557 
 558         /*
 559          * If we've already connected we will keep trying
 560          * until we time out, or the user gives up.
 561          */
 562 
 563         if (code < 13)
 564         {
 565                 if(icmp_err_convert[code].fatal || sk->state == TCP_SYN_SENT || sk->state == TCP_SYN_RECV)
 566                 {
 567                         sk->err = icmp_err_convert[code].errno;
 568                         if (sk->state == TCP_SYN_SENT || sk->state == TCP_SYN_RECV)
 569                         {
 570                                 tcp_statistics.TcpAttemptFails++;
 571                                 tcp_set_state(sk,TCP_CLOSE);
 572                                 sk->error_report(sk);           /* Wake people up to see the error (see connect in sock.c) */
 573                         }
 574                 }
 575                 else    /* Only an error on timeout */
 576                         sk->err_soft = icmp_err_convert[code].errno;
 577         }
 578 }
 579 
 580 
 581 /*
 582  *      Walk down the receive queue counting readable data until we hit the end or we find a gap
 583  *      in the received data queue (ie a frame missing that needs sending to us). Not
 584  *      sorting using two queues as data arrives makes life so much harder.
 585  */
 586 
 587 static int tcp_readable(struct sock *sk)
     /* [previous][next][first][last][top][bottom][index][help] */
 588 {
 589         unsigned long counted;
 590         unsigned long amount;
 591         struct sk_buff *skb;
 592         int sum;
 593         unsigned long flags;
 594 
 595         if(sk && sk->debug)
 596                 printk("tcp_readable: %p - ",sk);
 597 
 598         save_flags(flags);
 599         cli();
 600         if (sk == NULL || (skb = skb_peek(&sk->receive_queue)) == NULL)
 601         {
 602                 restore_flags(flags);
 603                 if(sk && sk->debug)
 604                         printk("empty\n");
 605                 return(0);
 606         }
 607 
 608         counted = sk->copied_seq;       /* Where we are at the moment */
 609         amount = 0;
 610 
 611         /*
 612          *      Do until a push or until we are out of data.
 613          */
 614 
 615         do
 616         {
 617                 if (before(counted, skb->seq))          /* Found a hole so stops here */
 618                         break;
 619                 sum = skb->len - (counted - skb->seq);  /* Length - header but start from where we are up to (avoid overlaps) */
 620                 if (skb->h.th->syn)
 621                         sum++;
 622                 if (sum > 0)
 623                 {                                       /* Add it up, move on */
 624                         amount += sum;
 625                         if (skb->h.th->syn)
 626                                 amount--;
 627                         counted += sum;
 628                 }
 629                 /*
 630                  * Don't count urg data ... but do it in the right place!
 631                  * Consider: "old_data (ptr is here) URG PUSH data"
 632                  * The old code would stop at the first push because
 633                  * it counted the urg (amount==1) and then does amount--
 634                  * *after* the loop.  This means tcp_readable() always
 635                  * returned zero if any URG PUSH was in the queue, even
 636                  * though there was normal data available. If we subtract
 637                  * the urg data right here, we even get it to work for more
 638                  * than one URG PUSH skb without normal data.
 639                  * This means that select() finally works now with urg data
 640                  * in the queue.  Note that rlogin was never affected
 641                  * because it doesn't use select(); it uses two processes
 642                  * and a blocking read().  And the queue scan in tcp_read()
 643                  * was correct.  Mike <pall@rz.uni-karlsruhe.de>
 644                  */
 645                 if (skb->h.th->urg)
 646                         amount--;       /* don't count urg data */
 647                 if (amount && skb->h.th->psh) break;
 648                 skb = skb->next;
 649         }
 650         while(skb != (struct sk_buff *)&sk->receive_queue);
 651 
 652         restore_flags(flags);
 653         if(sk->debug)
 654                 printk("got %lu bytes.\n",amount);
 655         return(amount);
 656 }
 657 
 658 /*
 659  * LISTEN is a special case for select..
 660  */
 661 static int tcp_listen_select(struct sock *sk, int sel_type, select_table *wait)
     /* [previous][next][first][last][top][bottom][index][help] */
 662 {
 663         if (sel_type == SEL_IN) {
 664                 struct sk_buff * skb;
 665 
 666                 lock_sock(sk);
 667                 skb = tcp_find_established(sk);
 668                 release_sock(sk);
 669                 if (skb)
 670                         return 1;
 671                 select_wait(sk->sleep,wait);
 672                 return 0;
 673         }
 674         return 0;
 675 }
 676 
 677 
 678 /*
 679  *      Wait for a TCP event.
 680  *
 681  *      Note that we don't need to lock the socket, as the upper select layers
 682  *      take care of normal races (between the test and the event) and we don't
 683  *      go look at any of the socket buffers directly.
 684  */
 685 static int tcp_select(struct sock *sk, int sel_type, select_table *wait)
     /* [previous][next][first][last][top][bottom][index][help] */
 686 {
 687         if (sk->state == TCP_LISTEN)
 688                 return tcp_listen_select(sk, sel_type, wait);
 689 
 690         switch(sel_type) {
 691         case SEL_IN:
 692                 if (sk->err)
 693                         return 1;
 694                 if (sk->state == TCP_SYN_SENT || sk->state == TCP_SYN_RECV)
 695                         break;
 696 
 697                 if (sk->shutdown & RCV_SHUTDOWN)
 698                         return 1;
 699 
 700                 if (sk->acked_seq == sk->copied_seq)
 701                         break;
 702 
 703                 if (sk->urg_seq != sk->copied_seq ||
 704                     sk->acked_seq != sk->copied_seq+1 ||
 705                     sk->urginline || !sk->urg_data)
 706                         return 1;
 707                 break;
 708 
 709         case SEL_OUT:
 710                 if (sk->err)
 711                         return 1;
 712                 if (sk->shutdown & SEND_SHUTDOWN)
 713                         return 0;
 714                 if (sk->state == TCP_SYN_SENT || sk->state == TCP_SYN_RECV)
 715                         break;
 716                 /*
 717                  * This is now right thanks to a small fix
 718                  * by Matt Dillon.
 719                  */
 720 
 721                 if (sock_wspace(sk) < sk->mtu+128+sk->prot->max_header)
 722                         break;
 723                 return 1;
 724 
 725         case SEL_EX:
 726                 if (sk->urg_data)
 727                         return 1;
 728                 break;
 729         }
 730         select_wait(sk->sleep, wait);
 731         return 0;
 732 }
 733 
 734 int tcp_ioctl(struct sock *sk, int cmd, unsigned long arg)
     /* [previous][next][first][last][top][bottom][index][help] */
 735 {
 736         int err;
 737         switch(cmd)
 738         {
 739 
 740                 case TIOCINQ:
 741 #ifdef FIXME    /* FIXME: */
 742                 case FIONREAD:
 743 #endif
 744                 {
 745                         unsigned long amount;
 746 
 747                         if (sk->state == TCP_LISTEN)
 748                                 return(-EINVAL);
 749 
 750                         lock_sock(sk);
 751                         amount = tcp_readable(sk);
 752                         release_sock(sk);
 753                         err=verify_area(VERIFY_WRITE,(void *)arg, sizeof(int));
 754                         if(err)
 755                                 return err;
 756                         put_user(amount, (int *)arg);
 757                         return(0);
 758                 }
 759                 case SIOCATMARK:
 760                 {
 761                         int answ = sk->urg_data && sk->urg_seq == sk->copied_seq;
 762 
 763                         err = verify_area(VERIFY_WRITE,(void *) arg, sizeof(int));
 764                         if (err)
 765                                 return err;
 766                         put_user(answ,(int *) arg);
 767                         return(0);
 768                 }
 769                 case TIOCOUTQ:
 770                 {
 771                         unsigned long amount;
 772 
 773                         if (sk->state == TCP_LISTEN) return(-EINVAL);
 774                         amount = sock_wspace(sk);
 775                         err=verify_area(VERIFY_WRITE,(void *)arg, sizeof(int));
 776                         if(err)
 777                                 return err;
 778                         put_user(amount, (int *)arg);
 779                         return(0);
 780                 }
 781                 default:
 782                         return(-EINVAL);
 783         }
 784 }
 785 
 786 
 787 /*
 788  *      This routine computes a TCP checksum.
 789  *
 790  *      Modified January 1995 from a go-faster DOS routine by
 791  *      Jorge Cwik <jorge@laser.satlink.net>
 792  */
 793 #undef DEBUG_TCP_CHECK
 794 void tcp_send_check(struct tcphdr *th, unsigned long saddr,
     /* [previous][next][first][last][top][bottom][index][help] */
 795                 unsigned long daddr, int len, struct sk_buff *skb)
 796 {
 797 #ifdef DEBUG_TCP_CHECK
 798         u16 check;
 799 #endif
 800         th->check = 0;
 801         th->check = tcp_check(th, len, saddr, daddr,
 802                 csum_partial((char *)th,sizeof(*th),skb->csum));
 803 
 804 #ifdef DEBUG_TCP_CHECK
 805         check = th->check;
 806         th->check = 0;
 807         th->check = tcp_check(th, len, saddr, daddr,
 808                 csum_partial((char *)th,len,0));
 809         if (check != th->check) {
 810                 static int count = 0;
 811                 if (++count < 10) {
 812                         printk("Checksum %x (%x) from %p\n", th->check, check,
 813                                 (&th)[-1]);
 814                         printk("TCP=<off:%d a:%d s:%d f:%d>\n", th->doff*4, th->ack, th->syn, th->fin);
 815                 }
 816         }
 817 #endif
 818 }
 819 
 820 
 821 /*
 822  *      This routine builds a generic TCP header.
 823  */
 824 
 825 static inline int tcp_build_header(struct tcphdr *th, struct sock *sk, int push)
     /* [previous][next][first][last][top][bottom][index][help] */
 826 {
 827         memcpy(th,(void *) &(sk->dummy_th), sizeof(*th));
 828         th->psh = (push == 0) ? 1 : 0;
 829         th->seq = htonl(sk->write_seq);
 830         th->ack_seq = htonl(sk->acked_seq);
 831         th->window = htons(tcp_select_window(sk));
 832 
 833         return(sizeof(*th));
 834 }
 835 
 836 /*
 837  *      Wait for a socket to get into the connected state
 838  */
 839 static void wait_for_tcp_connect(struct sock * sk)
     /* [previous][next][first][last][top][bottom][index][help] */
 840 {
 841         release_sock(sk);
 842         cli();
 843         if (sk->state != TCP_ESTABLISHED && sk->state != TCP_CLOSE_WAIT && sk->err == 0)
 844         {
 845                 interruptible_sleep_on(sk->sleep);
 846         }
 847         sti();
 848         lock_sock(sk);
 849 }
 850 
 851 /*
 852  *      Wait for more memory for a socket
 853  */
 854 static void wait_for_tcp_memory(struct sock * sk)
     /* [previous][next][first][last][top][bottom][index][help] */
 855 {
 856         release_sock(sk);
 857         cli();
 858         if (sk->wmem_alloc*2 > sk->sndbuf &&
 859             (sk->state == TCP_ESTABLISHED||sk->state == TCP_CLOSE_WAIT)
 860                 && sk->err == 0)
 861         {
 862                 sk->socket->flags &= ~SO_NOSPACE;
 863                 interruptible_sleep_on(sk->sleep);
 864         }
 865         sti();
 866         lock_sock(sk);
 867 }
 868 
 869 
 870 /*
 871  *      This routine copies from a user buffer into a socket,
 872  *      and starts the transmit system.
 873  */
 874 
 875 static int do_tcp_sendmsg(struct sock *sk,
     /* [previous][next][first][last][top][bottom][index][help] */
 876         int iovlen, struct iovec *iov,
 877         int len, int nonblock, int flags)
 878 {
 879         int copied = 0;
 880         struct device *dev = NULL;
 881 
 882         /*
 883          *      Wait for a connection to finish.
 884          */
 885         while (sk->state != TCP_ESTABLISHED && sk->state != TCP_CLOSE_WAIT)
 886         {
 887                 if (sk->err)
 888                         return sock_error(sk);
 889 
 890                 if (sk->state != TCP_SYN_SENT && sk->state != TCP_SYN_RECV)
 891                 {
 892                         if (sk->keepopen)
 893                                 send_sig(SIGPIPE, current, 0);
 894                         return -EPIPE;
 895                 }
 896 
 897                 if (nonblock)
 898                         return -EAGAIN;
 899 
 900                 if (current->signal & ~current->blocked)
 901                         return -ERESTARTSYS;
 902 
 903                 wait_for_tcp_connect(sk);
 904         }
 905 
 906         /*
 907          *      Ok commence sending
 908          */
 909 
 910         while (--iovlen >= 0)
 911         {
 912                 int seglen=iov->iov_len;
 913                 unsigned char * from=iov->iov_base;
 914                 iov++;
 915 
 916                 while(seglen > 0)
 917                 {
 918                         int copy, delay;
 919                         int tmp;
 920                         struct sk_buff *skb;
 921 
 922                         /*
 923                          * Stop on errors
 924                          */
 925                         if (sk->err)
 926                         {
 927                                 if (copied)
 928                                         return copied;
 929                                 return sock_error(sk);
 930                         }
 931 
 932                         /*
 933                          *      Make sure that we are established.
 934                          */
 935                         if (sk->shutdown & SEND_SHUTDOWN)
 936                         {
 937                                 if (copied)
 938                                         return copied;
 939                                 return -EPIPE;
 940                         }
 941 
 942                 /*
 943                  * The following code can result in copy <= if sk->mss is ever
 944                  * decreased.  It shouldn't be.  sk->mss is min(sk->mtu, sk->max_window).
 945                  * sk->mtu is constant once SYN processing is finished.  I.e. we
 946                  * had better not get here until we've seen his SYN and at least one
 947                  * valid ack.  (The SYN sets sk->mtu and the ack sets sk->max_window.)
 948                  * But ESTABLISHED should guarantee that.  sk->max_window is by definition
 949                  * non-decreasing.  Note that any ioctl to set user_mss must be done
 950                  * before the exchange of SYN's.  If the initial ack from the other
 951                  * end has a window of 0, max_window and thus mss will both be 0.
 952                  */
 953 
 954                 /*
 955                  *      Now we need to check if we have a half built packet.
 956                  */
 957 #ifndef CONFIG_NO_PATH_MTU_DISCOVERY
 958                 /*
 959                  *      FIXME:  I'm almost sure that this fragment is BUG,
 960                  *              but it works... I do not know why 8) --ANK
 961                  *
 962                  *      Really, we should rebuild all the queues...
 963                  *      It's difficult. Temporary hack is to send all
 964                  *      queued segments with allowed fragmentation.
 965                  */
 966                 {
 967                         int new_mss = min(sk->mtu, sk->max_window);
 968                         if (new_mss < sk->mss)
 969                         {
 970                                 tcp_send_partial(sk);
 971                                 sk->mss = new_mss;
 972                         }
 973                 }
 974 #endif
 975 
 976                         if ((skb = tcp_dequeue_partial(sk)) != NULL)
 977                         {
 978                                 int tcp_size;
 979 
 980                                 tcp_size = skb->tail - (unsigned char *)(skb->h.th + 1);
 981 
 982                                 /* Add more stuff to the end of skb->len */
 983                                 if (!(flags & MSG_OOB))
 984                                 {
 985                                         copy = min(sk->mss - tcp_size, seglen);
 986                                         if (copy <= 0)
 987                                         {
 988                                                 printk("TCP: **bug**: \"copy\" <= 0\n");
 989                                                 return -EFAULT;
 990                                         }
 991                                         tcp_size += copy;
 992                                         memcpy_fromfs(skb_put(skb,copy), from, copy);
 993                                         skb->csum = csum_partial(skb->tail - tcp_size, tcp_size, 0);
 994                                         from += copy;
 995                                         copied += copy;
 996                                         len -= copy;
 997                                         sk->write_seq += copy;
 998                                         seglen -= copy;
 999                                 }
1000                                 if (tcp_size >= sk->mss || (flags & MSG_OOB) || !sk->packets_out)
1001                                         tcp_send_skb(sk, skb);
1002                                 else
1003                                         tcp_enqueue_partial(skb, sk);
1004                                 continue;
1005                         }
1006 
1007                 /*
1008                  * We also need to worry about the window.
1009                  * If window < 1/2 the maximum window we've seen from this
1010                  *   host, don't use it.  This is sender side
1011                  *   silly window prevention, as specified in RFC1122.
1012                  *   (Note that this is different than earlier versions of
1013                  *   SWS prevention, e.g. RFC813.).  What we actually do is
1014                  *   use the whole MSS.  Since the results in the right
1015                  *   edge of the packet being outside the window, it will
1016                  *   be queued for later rather than sent.
1017                  */
1018 
1019                         copy = sk->window_seq - sk->write_seq;
1020                         if (copy <= 0 || copy < (sk->max_window >> 1) || copy > sk->mss)
1021                                 copy = sk->mss;
1022                         if (copy > seglen)
1023                                 copy = seglen;
1024                         if (copy <= 0)
1025                         {
1026                                 printk("TCP: **bug**: copy=%d, sk->mss=%d\n", copy, sk->mss);
1027                                 return -EFAULT;
1028                         }
1029 
1030                         /*
1031                          *      We should really check the window here also.
1032                          */
1033 
1034                         delay = 0;
1035                         tmp = copy + sk->prot->max_header + 15;
1036                         if (copy < sk->mss && !(flags & MSG_OOB) && sk->packets_out)
1037                         {
1038                                 tmp = tmp - copy + sk->mtu + 128;
1039                                 delay = 1;
1040                         }
1041                         skb = sock_wmalloc(sk, tmp, 0, GFP_KERNEL);
1042 
1043                         /*
1044                          *      If we didn't get any memory, we need to sleep.
1045                          */
1046 
1047                         if (skb == NULL)
1048                         {
1049                                 sk->socket->flags |= SO_NOSPACE;
1050                                 if (nonblock)
1051                                 {
1052                                         if (copied)
1053                                                 return copied;
1054                                         return -EAGAIN;
1055                                 }
1056 
1057                                 if (current->signal & ~current->blocked)
1058                                 {
1059                                         if (copied)
1060                                                 return copied;
1061                                         return -ERESTARTSYS;
1062                                 }
1063 
1064                                 wait_for_tcp_memory(sk);
1065                                 continue;
1066                         }
1067 
1068                         skb->sk = sk;
1069                         skb->free = 0;
1070                         skb->localroute = sk->localroute|(flags&MSG_DONTROUTE);
1071 
1072                         /*
1073                          * FIXME: we need to optimize this.
1074                          * Perhaps some hints here would be good.
1075                          */
1076 
1077                         tmp = sk->prot->build_header(skb, sk->saddr, sk->daddr, &dev,
1078                                  IPPROTO_TCP, sk->opt, skb->truesize,sk->ip_tos,sk->ip_ttl,&sk->ip_route_cache);
1079                         if (tmp < 0 )
1080                         {
1081                                 sock_wfree(sk, skb);
1082                                 if (copied)
1083                                         return(copied);
1084                                 return(tmp);
1085                         }
1086 #ifndef CONFIG_NO_PATH_MTU_DISCOVERY
1087                         skb->ip_hdr->frag_off |= htons(IP_DF);
1088 #endif
1089                         skb->dev = dev;
1090                         skb->h.th =(struct tcphdr *)skb_put(skb,sizeof(struct tcphdr));
1091                         tmp = tcp_build_header(skb->h.th, sk, seglen-copy);
1092                         if (tmp < 0)
1093                         {
1094                                 sock_wfree(sk, skb);
1095                                 if (copied)
1096                                         return(copied);
1097                                 return(tmp);
1098                         }
1099 
1100                         if (flags & MSG_OOB)
1101                         {
1102                                 skb->h.th->urg = 1;
1103                                 skb->h.th->urg_ptr = ntohs(copy);
1104                         }
1105 
1106                         skb->csum = csum_partial_copy_fromuser(from,
1107                                 skb_put(skb,copy), copy, 0);
1108 
1109                         from += copy;
1110                         copied += copy;
1111                         len -= copy;
1112                         seglen -= copy;
1113                         skb->free = 0;
1114                         sk->write_seq += copy;
1115 
1116                         if (delay)
1117                         {
1118                                 tcp_enqueue_partial(skb, sk);
1119                                 continue;
1120                         }
1121                         tcp_send_skb(sk, skb);
1122                 }
1123         }
1124         sk->err = 0;
1125 
1126         return copied;
1127 }
1128 
1129 
1130 static int tcp_sendmsg(struct sock *sk, struct msghdr *msg,
     /* [previous][next][first][last][top][bottom][index][help] */
1131           int len, int nonblock, int flags)
1132 {
1133         int retval = -EINVAL;
1134 
1135         /*
1136          *      Do sanity checking for sendmsg/sendto/send
1137          */
1138 
1139         if (flags & ~(MSG_OOB|MSG_DONTROUTE))
1140                 goto out;
1141         if (msg->msg_name) {
1142                 struct sockaddr_in *addr=(struct sockaddr_in *)msg->msg_name;
1143 
1144                 if (msg->msg_namelen < sizeof(*addr))
1145                         goto out;
1146                 if (addr->sin_family && addr->sin_family != AF_INET)
1147                         goto out;
1148                 retval = -ENOTCONN;
1149                 if(sk->state == TCP_CLOSE)
1150                         goto out;
1151                 retval = -EISCONN;
1152                 if (addr->sin_port != sk->dummy_th.dest)
1153                         goto out;
1154                 if (addr->sin_addr.s_addr != sk->daddr)
1155                         goto out;
1156         }
1157 
1158         lock_sock(sk);
1159         retval = do_tcp_sendmsg(sk, msg->msg_iovlen, msg->msg_iov, len, nonblock, flags);
1160 
1161 /*
1162  *      Nagle's rule. Turn Nagle off with TCP_NODELAY for highly
1163  *      interactive fast network servers. It's meant to be on and
1164  *      it really improves the throughput though not the echo time
1165  *      on my slow slip link - Alan
1166  *
1167  *      If not nagling we can send on the before case too..
1168  */
1169 
1170         if (sk->partial) {
1171                 if (!sk->packets_out ||
1172                     (sk->nonagle && before(sk->write_seq , sk->window_seq))) {
1173                         tcp_send_partial(sk);
1174                 }
1175         }
1176 
1177         release_sock(sk);
1178 
1179 out:
1180         return retval;
1181 }
1182 
1183 
1184 /*
1185  *      Send an ack if one is backlogged at this point.
1186  *
1187  *      This is called for delayed acks also.
1188  */
1189 
1190 void tcp_read_wakeup(struct sock *sk)
     /* [previous][next][first][last][top][bottom][index][help] */
1191 {
1192         if (!sk->ack_backlog)
1193                 return;
1194 
1195         /*
1196          * If we're closed, don't send an ack, or we'll get a RST
1197          * from the closed destination.
1198          */
1199         if ((sk->state == TCP_CLOSE) || (sk->state == TCP_TIME_WAIT))
1200                 return;
1201 
1202         tcp_send_ack(sk);
1203 }
1204 
1205 
1206 /*
1207  *      Handle reading urgent data. BSD has very simple semantics for
1208  *      this, no blocking and very strange errors 8)
1209  */
1210 
1211 static int tcp_recv_urg(struct sock * sk, int nonblock,
     /* [previous][next][first][last][top][bottom][index][help] */
1212              struct msghdr *msg, int len, int flags, int *addr_len)
1213 {
1214         /*
1215          *      No URG data to read
1216          */
1217         if (sk->urginline || !sk->urg_data || sk->urg_data == URG_READ)
1218                 return -EINVAL; /* Yes this is right ! */
1219 
1220         if (sk->err)
1221                 return sock_error(sk);
1222 
1223         if (sk->state == TCP_CLOSE || sk->done)
1224         {
1225                 if (!sk->done)
1226                 {
1227                         sk->done = 1;
1228                         return 0;
1229                 }
1230                 return -ENOTCONN;
1231         }
1232 
1233         if (sk->shutdown & RCV_SHUTDOWN)
1234         {
1235                 sk->done = 1;
1236                 return 0;
1237         }
1238         lock_sock(sk);
1239         if (sk->urg_data & URG_VALID)
1240         {
1241                 char c = sk->urg_data;
1242                 if (!(flags & MSG_PEEK))
1243                         sk->urg_data = URG_READ;
1244                 memcpy_toiovec(msg->msg_iov, &c, 1);
1245                 if(msg->msg_name)
1246                 {
1247                         struct sockaddr_in *sin=(struct sockaddr_in *)msg->msg_name;
1248                         sin->sin_family=AF_INET;
1249                         sin->sin_addr.s_addr=sk->daddr;
1250                         sin->sin_port=sk->dummy_th.dest;
1251                 }
1252                 if(addr_len)
1253                         *addr_len=sizeof(struct sockaddr_in);
1254                 release_sock(sk);
1255                 return 1;
1256         }
1257         release_sock(sk);
1258 
1259         /*
1260          * Fixed the recv(..., MSG_OOB) behaviour.  BSD docs and
1261          * the available implementations agree in this case:
1262          * this call should never block, independent of the
1263          * blocking state of the socket.
1264          * Mike <pall@rz.uni-karlsruhe.de>
1265          */
1266         return -EAGAIN;
1267 }
1268 
1269 /*
1270  *      Release a skb if it is no longer needed. This routine
1271  *      must be called with interrupts disabled or with the
1272  *      socket locked so that the sk_buff queue operation is ok.
1273  */
1274 
1275 static inline void tcp_eat_skb(struct sock *sk, struct sk_buff * skb)
     /* [previous][next][first][last][top][bottom][index][help] */
1276 {
1277         skb->sk = sk;
1278         __skb_unlink(skb, &sk->receive_queue);
1279         kfree_skb(skb, FREE_READ);
1280 }
1281 
1282 /*
1283  *      FIXME:
1284  *      This routine frees used buffers.
1285  *      It should consider sending an ACK to let the
1286  *      other end know we now have a bigger window.
1287  */
1288 
1289 static void cleanup_rbuf(struct sock *sk)
     /* [previous][next][first][last][top][bottom][index][help] */
1290 {
1291         /*
1292          * NOTE! The socket must be locked, so that we don't get
1293          * a messed-up receive queue.
1294          */
1295         while (!skb_queue_empty(&sk->receive_queue)) {
1296                 struct sk_buff *skb = sk->receive_queue.next;
1297                 if (!skb->used || skb->users)
1298                         break;
1299                 tcp_eat_skb(sk, skb);
1300         }
1301 
1302         /*
1303          * Tell the world if we raised the window.
1304          */
1305         if (tcp_raise_window(sk))
1306                 tcp_send_ack(sk);
1307 }
1308 
1309 
1310 /*
1311  *      This routine copies from a sock struct into the user buffer.
1312  */
1313 
1314 static int tcp_recvmsg(struct sock *sk, struct msghdr *msg,
     /* [previous][next][first][last][top][bottom][index][help] */
1315         int len, int nonblock, int flags, int *addr_len)
1316 {
1317         struct wait_queue wait = { current, NULL };
1318         int copied = 0;
1319         u32 peek_seq;
1320         volatile u32 *seq;      /* So gcc doesn't overoptimise */
1321         unsigned long used;
1322 
1323         /*
1324          *      This error should be checked.
1325          */
1326 
1327         if (sk->state == TCP_LISTEN)
1328                 return -ENOTCONN;
1329 
1330         /*
1331          *      Urgent data needs to be handled specially.
1332          */
1333 
1334         if (flags & MSG_OOB)
1335                 return tcp_recv_urg(sk, nonblock, msg, len, flags, addr_len);
1336 
1337         /*
1338          *      Copying sequence to update. This is volatile to handle
1339          *      the multi-reader case neatly (memcpy_to/fromfs might be
1340          *      inline and thus not flush cached variables otherwise).
1341          */
1342 
1343         peek_seq = sk->copied_seq;
1344         seq = &sk->copied_seq;
1345         if (flags & MSG_PEEK)
1346                 seq = &peek_seq;
1347 
1348         add_wait_queue(sk->sleep, &wait);
1349         lock_sock(sk);
1350         while (len > 0)
1351         {
1352                 struct sk_buff * skb;
1353                 u32 offset;
1354 
1355                 /*
1356                  * Are we at urgent data? Stop if we have read anything.
1357                  */
1358 
1359                 if (copied && sk->urg_data && sk->urg_seq == *seq)
1360                         break;
1361 
1362                 /*
1363                  * We need to check signals first, to get correct SIGURG
1364                  * handling.
1365                  */
1366                 if (current->signal & ~current->blocked) {
1367                         if (copied)
1368                                 break;
1369                         copied = -ERESTARTSYS;
1370                         break;
1371                 }
1372 
1373                 /*
1374                  *      Next get a buffer.
1375                  */
1376 
1377                 current->state = TASK_INTERRUPTIBLE;
1378 
1379                 skb = skb_peek(&sk->receive_queue);
1380                 do
1381                 {
1382                         if (!skb)
1383                                 break;
1384                         if (before(*seq, skb->seq))
1385                                 break;
1386                         offset = *seq - skb->seq;
1387                         if (skb->h.th->syn)
1388                                 offset--;
1389                         if (offset < skb->len)
1390                                 goto found_ok_skb;
1391                         if (skb->h.th->fin)
1392                                 goto found_fin_ok;
1393                         if (!(flags & MSG_PEEK))
1394                                 skb->used = 1;
1395                         skb = skb->next;
1396                 }
1397                 while (skb != (struct sk_buff *)&sk->receive_queue);
1398 
1399                 if (copied)
1400                         break;
1401 
1402                 if (sk->err)
1403                 {
1404                         copied = sock_error(sk);
1405                         break;
1406                 }
1407 
1408                 if (sk->state == TCP_CLOSE)
1409                 {
1410                         if (!sk->done)
1411                         {
1412                                 sk->done = 1;
1413                                 break;
1414                         }
1415                         copied = -ENOTCONN;
1416                         break;
1417                 }
1418 
1419                 if (sk->shutdown & RCV_SHUTDOWN)
1420                 {
1421                         sk->done = 1;
1422                         break;
1423                 }
1424 
1425                 if (nonblock)
1426                 {
1427                         copied = -EAGAIN;
1428                         break;
1429                 }
1430 
1431                 cleanup_rbuf(sk);
1432                 release_sock(sk);
1433                 sk->socket->flags |= SO_WAITDATA;
1434                 schedule();
1435                 sk->socket->flags &= ~SO_WAITDATA;
1436                 lock_sock(sk);
1437                 continue;
1438 
1439         found_ok_skb:
1440                 /*
1441                  *      Lock the buffer. We can be fairly relaxed as
1442                  *      an interrupt will never steal a buffer we are
1443                  *      using unless I've missed something serious in
1444                  *      tcp_data.
1445                  */
1446 
1447                 skb->users++;
1448 
1449                 /*
1450                  *      Ok so how much can we use ?
1451                  */
1452 
1453                 used = skb->len - offset;
1454                 if (len < used)
1455                         used = len;
1456                 /*
1457                  *      Do we have urgent data here?
1458                  */
1459 
1460                 if (sk->urg_data)
1461                 {
1462                         u32 urg_offset = sk->urg_seq - *seq;
1463                         if (urg_offset < used)
1464                         {
1465                                 if (!urg_offset)
1466                                 {
1467                                         if (!sk->urginline)
1468                                         {
1469                                                 ++*seq;
1470                                                 offset++;
1471                                                 used--;
1472                                         }
1473                                 }
1474                                 else
1475                                         used = urg_offset;
1476                         }
1477                 }
1478 
1479                 /*
1480                  *      Copy it - We _MUST_ update *seq first so that we
1481                  *      don't ever double read when we have dual readers
1482                  */
1483 
1484                 *seq += used;
1485 
1486                 /*
1487                  *      This memcpy_tofs can sleep. If it sleeps and we
1488                  *      do a second read it relies on the skb->users to avoid
1489                  *      a crash when cleanup_rbuf() gets called.
1490                  */
1491 
1492                 memcpy_toiovec(msg->msg_iov,((unsigned char *)skb->h.th) +
1493                         skb->h.th->doff*4 + offset, used);
1494                 copied += used;
1495                 len -= used;
1496 
1497                 /*
1498                  *      We now will not sleep again until we are finished
1499                  *      with skb. Sorry if you are doing the SMP port
1500                  *      but you'll just have to fix it neatly ;)
1501                  */
1502 
1503                 skb->users --;
1504 
1505                 if (after(sk->copied_seq,sk->urg_seq))
1506                         sk->urg_data = 0;
1507                 if (used + offset < skb->len)
1508                         continue;
1509 
1510                 /*
1511                  *      Process the FIN.
1512                  */
1513 
1514                 if (skb->h.th->fin)
1515                         goto found_fin_ok;
1516                 if (flags & MSG_PEEK)
1517                         continue;
1518                 skb->used = 1;
1519                 if (!skb->users)
1520                         tcp_eat_skb(sk, skb);
1521                 continue;
1522 
1523         found_fin_ok:
1524                 ++*seq;
1525                 if (flags & MSG_PEEK)
1526                         break;
1527 
1528                 /*
1529                  *      All is done
1530                  */
1531 
1532                 skb->used = 1;
1533                 sk->shutdown |= RCV_SHUTDOWN;
1534                 break;
1535 
1536         }
1537 
1538         if(copied>0 && msg->msg_name)
1539         {
1540                 struct sockaddr_in *sin=(struct sockaddr_in *)msg->msg_name;
1541                 sin->sin_family=AF_INET;
1542                 sin->sin_addr.s_addr=sk->daddr;
1543                 sin->sin_port=sk->dummy_th.dest;
1544         }
1545         if(addr_len)
1546                 *addr_len=sizeof(struct sockaddr_in);
1547 
1548         remove_wait_queue(sk->sleep, &wait);
1549         current->state = TASK_RUNNING;
1550 
1551         /* Clean up data we have read: This will do ACK frames */
1552         cleanup_rbuf(sk);
1553         release_sock(sk);
1554         return copied;
1555 }
1556 
1557 
1558 
1559 /*
1560  *      State processing on a close. This implements the state shift for
1561  *      sending our FIN frame. Note that we only send a FIN for some
1562  *      states. A shutdown() may have already sent the FIN, or we may be
1563  *      closed.
1564  */
1565 
1566 static int tcp_close_state(struct sock *sk, int dead)
     /* [previous][next][first][last][top][bottom][index][help] */
1567 {
1568         int ns=TCP_CLOSE;
1569         int send_fin=0;
1570         switch(sk->state)
1571         {
1572                 case TCP_SYN_SENT:      /* No SYN back, no FIN needed */
1573                         break;
1574                 case TCP_SYN_RECV:
1575                 case TCP_ESTABLISHED:   /* Closedown begin */
1576                         ns=TCP_FIN_WAIT1;
1577                         send_fin=1;
1578                         break;
1579                 case TCP_FIN_WAIT1:     /* Already closing, or FIN sent: no change */
1580                 case TCP_FIN_WAIT2:
1581                 case TCP_CLOSING:
1582                         ns=sk->state;
1583                         break;
1584                 case TCP_CLOSE:
1585                 case TCP_LISTEN:
1586                         break;
1587                 case TCP_CLOSE_WAIT:    /* They have FIN'd us. We send our FIN and
1588                                            wait only for the ACK */
1589                         ns=TCP_LAST_ACK;
1590                         send_fin=1;
1591         }
1592 
1593         tcp_set_state(sk,ns);
1594 
1595         /*
1596          *      This is a (useful) BSD violating of the RFC. There is a
1597          *      problem with TCP as specified in that the other end could
1598          *      keep a socket open forever with no application left this end.
1599          *      We use a 3 minute timeout (about the same as BSD) then kill
1600          *      our end. If they send after that then tough - BUT: long enough
1601          *      that we won't make the old 4*rto = almost no time - whoops
1602          *      reset mistake.
1603          */
1604         if(dead && ns==TCP_FIN_WAIT2)
1605         {
1606                 int timer_active=del_timer(&sk->timer);
1607                 if(timer_active)
1608                         add_timer(&sk->timer);
1609                 else
1610                         tcp_reset_msl_timer(sk, TIME_CLOSE, TCP_FIN_TIMEOUT);
1611         }
1612 
1613         return send_fin;
1614 }
1615 
1616 /*
1617  *      Shutdown the sending side of a connection. Much like close except
1618  *      that we don't receive shut down or set sk->dead.
1619  */
1620 
1621 void tcp_shutdown(struct sock *sk, int how)
     /* [previous][next][first][last][top][bottom][index][help] */
1622 {
1623         /*
1624          *      We need to grab some memory, and put together a FIN,
1625          *      and then put it into the queue to be sent.
1626          *              Tim MacKenzie(tym@dibbler.cs.monash.edu.au) 4 Dec '92.
1627          */
1628 
1629         if (!(how & SEND_SHUTDOWN))
1630                 return;
1631 
1632         /*
1633          *      If we've already sent a FIN, or it's a closed state
1634          */
1635 
1636         if (sk->state == TCP_FIN_WAIT1 ||
1637             sk->state == TCP_FIN_WAIT2 ||
1638             sk->state == TCP_CLOSING ||
1639             sk->state == TCP_LAST_ACK ||
1640             sk->state == TCP_TIME_WAIT ||
1641             sk->state == TCP_CLOSE ||
1642             sk->state == TCP_LISTEN
1643           )
1644         {
1645                 return;
1646         }
1647         lock_sock(sk);
1648 
1649         /*
1650          * flag that the sender has shutdown
1651          */
1652 
1653         sk->shutdown |= SEND_SHUTDOWN;
1654 
1655         /*
1656          *  Clear out any half completed packets.
1657          */
1658 
1659         if (sk->partial)
1660                 tcp_send_partial(sk);
1661 
1662         /*
1663          *      FIN if needed
1664          */
1665 
1666         if (tcp_close_state(sk,0))
1667                 tcp_send_fin(sk);
1668 
1669         release_sock(sk);
1670 }
1671 
1672 
1673 /*
1674  *      Return 1 if we still have things to send in our buffers.
1675  */
1676 
1677 static inline int closing(struct sock * sk)
     /* [previous][next][first][last][top][bottom][index][help] */
1678 {
1679         switch (sk->state) {
1680                 case TCP_FIN_WAIT1:
1681                 case TCP_CLOSING:
1682                 case TCP_LAST_ACK:
1683                         return 1;
1684         }
1685         return 0;
1686 }
1687 
1688 
1689 static void tcp_close(struct sock *sk, unsigned long timeout)
     /* [previous][next][first][last][top][bottom][index][help] */
1690 {
1691         struct sk_buff *skb;
1692 
1693         /*
1694          * We need to grab some memory, and put together a FIN,
1695          * and then put it into the queue to be sent.
1696          */
1697 
1698         lock_sock(sk);
1699 
1700         tcp_cache_zap();
1701         if(sk->state == TCP_LISTEN)
1702         {
1703                 /* Special case */
1704                 tcp_set_state(sk, TCP_CLOSE);
1705                 tcp_close_pending(sk);
1706                 release_sock(sk);
1707                 sk->dead = 1;
1708                 return;
1709         }
1710 
1711         sk->keepopen = 1;
1712         sk->shutdown = SHUTDOWN_MASK;
1713 
1714         if (!sk->dead)
1715                 sk->state_change(sk);
1716 
1717         /*
1718          *  We need to flush the recv. buffs.  We do this only on the
1719          *  descriptor close, not protocol-sourced closes, because the
1720          *  reader process may not have drained the data yet!
1721          */
1722 
1723         while((skb=skb_dequeue(&sk->receive_queue))!=NULL)
1724                 kfree_skb(skb, FREE_READ);
1725 
1726         /*
1727          *      Get rid off any half-completed packets.
1728          */
1729 
1730         if (sk->partial)
1731                 tcp_send_partial(sk);
1732 
1733         /*
1734          *      Timeout is not the same thing - however the code likes
1735          *      to send both the same way (sigh).
1736          */
1737 
1738         if (tcp_close_state(sk,1)==1)
1739         {
1740                 tcp_send_fin(sk);
1741         }
1742 
1743         if (timeout) {
1744                 cli();
1745                 release_sock(sk);
1746                 current->timeout = timeout;
1747                 while(closing(sk) && current->timeout)
1748                 {
1749                         interruptible_sleep_on(sk->sleep);
1750                         if (current->signal & ~current->blocked)
1751                         {
1752                                 break;
1753                         }
1754                 }
1755                 current->timeout=0;
1756                 lock_sock(sk);
1757                 sti();
1758         }
1759 
1760         /*
1761          * This will destroy it. The timers will take care of actually
1762          * free'ing up the memory.
1763          */
1764         tcp_cache_zap();        /* Kill the cache again. */
1765         release_sock(sk);
1766         sk->dead = 1;
1767 }
1768 
1769 
1770 /*
1771  * Wait for a incoming connection, avoid race
1772  * conditions. This must be called with the socket
1773  * locked.
1774  */
1775 static struct sk_buff * wait_for_connect(struct sock * sk)
     /* [previous][next][first][last][top][bottom][index][help] */
1776 {
1777         struct wait_queue wait = { current, NULL };
1778         struct sk_buff * skb = NULL;
1779 
1780         add_wait_queue(sk->sleep, &wait);
1781         for (;;) {
1782                 current->state = TASK_INTERRUPTIBLE;
1783                 release_sock(sk);
1784                 schedule();
1785                 lock_sock(sk);
1786                 skb = tcp_find_established(sk);
1787                 if (skb)
1788                         break;
1789                 if (current->signal & ~current->blocked)
1790                         break;
1791         }
1792         remove_wait_queue(sk->sleep, &wait);
1793         return skb;
1794 }
1795 
1796 /*
1797  *      This will accept the next outstanding connection.
1798  *
1799  *      Be careful about race conditions here - this is subtle.
1800  */
1801 
1802 static struct sock *tcp_accept(struct sock *sk, int flags)
     /* [previous][next][first][last][top][bottom][index][help] */
1803 {
1804         int error;
1805         struct sk_buff *skb;
1806         struct sock *newsk = NULL;
1807 
1808   /*
1809    * We need to make sure that this socket is listening,
1810    * and that it has something pending.
1811    */
1812 
1813         error = EINVAL;
1814         if (sk->state != TCP_LISTEN)
1815                 goto no_listen;
1816 
1817         lock_sock(sk);
1818 
1819         skb = tcp_find_established(sk);
1820         if (skb) {
1821 got_new_connect:
1822                 __skb_unlink(skb, &sk->receive_queue);
1823                 newsk = skb->sk;
1824                 kfree_skb(skb, FREE_READ);
1825                 sk->ack_backlog--;
1826                 error = 0;
1827 out:
1828                 release_sock(sk);
1829 no_listen:
1830                 sk->err = error;
1831                 return newsk;
1832         }
1833 
1834         error = EAGAIN;
1835         if (flags & O_NONBLOCK)
1836                 goto out;
1837         skb = wait_for_connect(sk);
1838         if (skb)
1839                 goto got_new_connect;
1840         error = ERESTARTSYS;
1841         goto out;
1842 }
1843 
1844 
1845 /*
1846  *      This will initiate an outgoing connection.
1847  */
1848 
1849 static int tcp_connect(struct sock *sk, struct sockaddr_in *usin, int addr_len)
     /* [previous][next][first][last][top][bottom][index][help] */
1850 {
1851         struct sk_buff *buff;
1852         struct device *dev=NULL;
1853         unsigned char *ptr;
1854         int tmp;
1855         int atype;
1856         struct tcphdr *t1;
1857         struct rtable *rt;
1858 
1859         if (sk->state != TCP_CLOSE)
1860                 return(-EISCONN);
1861 
1862         /*
1863          *      Don't allow a double connect.
1864          */
1865 
1866         if(sk->daddr)
1867                 return -EINVAL;
1868 
1869         if (addr_len < 8)
1870                 return(-EINVAL);
1871 
1872         if (usin->sin_family && usin->sin_family != AF_INET)
1873                 return(-EAFNOSUPPORT);
1874 
1875         /*
1876          *      connect() to INADDR_ANY means loopback (BSD'ism).
1877          */
1878 
1879         if(usin->sin_addr.s_addr==INADDR_ANY)
1880                 usin->sin_addr.s_addr=ip_my_addr();
1881 
1882         /*
1883          *      Don't want a TCP connection going to a broadcast address
1884          */
1885 
1886         if ((atype=ip_chk_addr(usin->sin_addr.s_addr)) == IS_BROADCAST || atype==IS_MULTICAST)
1887                 return -ENETUNREACH;
1888 
1889         lock_sock(sk);
1890         sk->daddr = usin->sin_addr.s_addr;
1891         sk->write_seq = tcp_init_seq();
1892         sk->window_seq = sk->write_seq;
1893         sk->rcv_ack_seq = sk->write_seq -1;
1894         sk->rcv_ack_cnt = 1;
1895         sk->err = 0;
1896         sk->dummy_th.dest = usin->sin_port;
1897         release_sock(sk);
1898 
1899         buff = sock_wmalloc(sk,MAX_SYN_SIZE,0, GFP_KERNEL);
1900         if (buff == NULL)
1901         {
1902                 return(-ENOMEM);
1903         }
1904         lock_sock(sk);
1905         buff->sk = sk;
1906         buff->free = 0;
1907         buff->localroute = sk->localroute;
1908 
1909 
1910         /*
1911          *      Put in the IP header and routing stuff.
1912          */
1913 
1914         tmp = sk->prot->build_header(buff, sk->saddr, sk->daddr, &dev,
1915                 IPPROTO_TCP, sk->opt, MAX_SYN_SIZE,sk->ip_tos,sk->ip_ttl,&sk->ip_route_cache);
1916         if (tmp < 0)
1917         {
1918                 sock_wfree(sk, buff);
1919                 release_sock(sk);
1920                 return(-ENETUNREACH);
1921         }
1922         if ((rt = sk->ip_route_cache) != NULL && !sk->saddr)
1923                 sk->saddr = rt->rt_src;
1924         sk->rcv_saddr = sk->saddr;
1925 
1926         t1 = (struct tcphdr *) skb_put(buff,sizeof(struct tcphdr));
1927 
1928         memcpy(t1,(void *)&(sk->dummy_th), sizeof(*t1));
1929         buff->seq = sk->write_seq++;
1930         t1->seq = htonl(buff->seq);
1931         sk->sent_seq = sk->write_seq;
1932         buff->end_seq = sk->write_seq;
1933         t1->ack = 0;
1934         t1->window = 2;
1935         t1->syn = 1;
1936         t1->doff = 6;
1937         /* use 512 or whatever user asked for */
1938 
1939         if(rt!=NULL && (rt->rt_flags&RTF_WINDOW))
1940                 sk->window_clamp=rt->rt_window;
1941         else
1942                 sk->window_clamp=0;
1943 
1944         if (sk->user_mss)
1945                 sk->mtu = sk->user_mss;
1946         else if (rt)
1947                 sk->mtu = rt->rt_mtu - sizeof(struct iphdr) - sizeof(struct tcphdr);
1948         else
1949                 sk->mtu = 576 - sizeof(struct iphdr) - sizeof(struct tcphdr);
1950 
1951         /*
1952          *      but not bigger than device MTU
1953          */
1954 
1955         if(sk->mtu <32)
1956                 sk->mtu = 32;   /* Sanity limit */
1957 
1958         sk->mtu = min(sk->mtu, dev->mtu - sizeof(struct iphdr) - sizeof(struct tcphdr));
1959 
1960 #ifdef CONFIG_SKIP
1961 
1962         /*
1963          *      SKIP devices set their MTU to 65535. This is so they can take packets
1964          *      unfragmented to security process then fragment. They could lie to the
1965          *      TCP layer about a suitable MTU, but its easier to let skip sort it out
1966          *      simply because the final package we want unfragmented is going to be
1967          *
1968          *      [IPHDR][IPSP][Security data][Modified TCP data][Security data]
1969          */
1970 
1971         if(skip_pick_mtu!=NULL)         /* If SKIP is loaded.. */
1972                 sk->mtu=skip_pick_mtu(sk->mtu,dev);
1973 #endif
1974 
1975         /*
1976          *      Put in the TCP options to say MTU.
1977          */
1978 
1979         ptr = skb_put(buff,4);
1980         ptr[0] = 2;
1981         ptr[1] = 4;
1982         ptr[2] = (sk->mtu) >> 8;
1983         ptr[3] = (sk->mtu) & 0xff;
1984         buff->csum = csum_partial(ptr, 4, 0);
1985         tcp_send_check(t1, sk->saddr, sk->daddr,
1986                   sizeof(struct tcphdr) + 4, buff);
1987 
1988         /*
1989          *      This must go first otherwise a really quick response will get reset.
1990          */
1991 
1992         tcp_cache_zap();
1993         tcp_set_state(sk,TCP_SYN_SENT);
1994         if(rt&&rt->rt_flags&RTF_IRTT)
1995                 sk->rto = rt->rt_irtt;
1996         else
1997                 sk->rto = TCP_TIMEOUT_INIT;
1998         sk->delack_timer.function = tcp_delack_timer;
1999         sk->delack_timer.data = (unsigned long) sk;
2000         sk->retransmit_timer.function = tcp_retransmit_timer;
2001         sk->retransmit_timer.data = (unsigned long)sk;
2002         tcp_reset_xmit_timer(sk, TIME_WRITE, sk->rto);  /* Timer for repeating the SYN until an answer  */
2003         sk->retransmits = 0;                            /* Now works the right way instead of a hacked
2004                                                                                         initial setting */
2005 
2006         sk->prot->queue_xmit(sk, dev, buff, 0);
2007         tcp_reset_xmit_timer(sk, TIME_WRITE, sk->rto);
2008         tcp_statistics.TcpActiveOpens++;
2009         tcp_statistics.TcpOutSegs++;
2010 
2011         release_sock(sk);
2012         return(0);
2013 }
2014 
2015 /*
2016  *      Socket option code for TCP.
2017  */
2018 
2019 int tcp_setsockopt(struct sock *sk, int level, int optname, char *optval, int optlen)
     /* [previous][next][first][last][top][bottom][index][help] */
2020 {
2021         int val,err;
2022 
2023         if(level!=SOL_TCP)
2024                 return ip_setsockopt(sk,level,optname,optval,optlen);
2025 
2026         if (optval == NULL)
2027                 return(-EINVAL);
2028 
2029         err=verify_area(VERIFY_READ, optval, sizeof(int));
2030         if(err)
2031                 return err;
2032 
2033         val = get_user((int *)optval);
2034 
2035         switch(optname)
2036         {
2037                 case TCP_MAXSEG:
2038 /*
2039  * values greater than interface MTU won't take effect.  however at
2040  * the point when this call is done we typically don't yet know
2041  * which interface is going to be used
2042  */
2043                         if(val<1||val>MAX_WINDOW)
2044                                 return -EINVAL;
2045                         sk->user_mss=val;
2046                         return 0;
2047                 case TCP_NODELAY:
2048                         sk->nonagle=(val==0)?0:1;
2049                         return 0;
2050                 default:
2051                         return(-ENOPROTOOPT);
2052         }
2053 }
2054 
2055 int tcp_getsockopt(struct sock *sk, int level, int optname, char *optval, int *optlen)
     /* [previous][next][first][last][top][bottom][index][help] */
2056 {
2057         int val,err;
2058 
2059         if(level!=SOL_TCP)
2060                 return ip_getsockopt(sk,level,optname,optval,optlen);
2061 
2062         switch(optname)
2063         {
2064                 case TCP_MAXSEG:
2065                         val=sk->user_mss;
2066                         break;
2067                 case TCP_NODELAY:
2068                         val=sk->nonagle;
2069                         break;
2070                 default:
2071                         return(-ENOPROTOOPT);
2072         }
2073         err=verify_area(VERIFY_WRITE, optlen, sizeof(int));
2074         if(err)
2075                 return err;
2076         put_user(sizeof(int),(int *) optlen);
2077 
2078         err=verify_area(VERIFY_WRITE, optval, sizeof(int));
2079         if(err)
2080                 return err;
2081         put_user(val,(int *)optval);
2082 
2083         return(0);
2084 }
2085 
2086 
2087 struct proto tcp_prot = {
2088         tcp_close,
2089         ip_build_header,
2090         tcp_connect,
2091         tcp_accept,
2092         ip_queue_xmit,
2093         tcp_retransmit,
2094         tcp_write_wakeup,
2095         tcp_read_wakeup,
2096         tcp_rcv,
2097         tcp_select,
2098         tcp_ioctl,
2099         NULL,
2100         tcp_shutdown,
2101         tcp_setsockopt,
2102         tcp_getsockopt,
2103         tcp_sendmsg,
2104         tcp_recvmsg,
2105         NULL,           /* No special bind() */
2106         128,
2107         0,
2108         "TCP",
2109         0, 0,
2110         {NULL,}
2111 };

/* [previous][next][first][last][top][bottom][index][help] */