root/net/ipv4/packet.c

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DEFINITIONS

This source file includes following definitions.
  1. min
  2. packet_rcv
  3. packet_sendto
  4. packet_write
  5. packet_close
  6. packet_init
  7. packet_recvfrom
  8. packet_read

   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  *              PACKET - implements raw packet sockets.
   7  *
   8  * Version:     @(#)packet.c    1.0.6   05/25/93
   9  *
  10  * Authors:     Ross Biro, <bir7@leland.Stanford.Edu>
  11  *              Fred N. van Kempen, <waltje@uWalt.NL.Mugnet.ORG>
  12  *              Alan Cox, <gw4pts@gw4pts.ampr.org>
  13  *
  14  * Fixes:       
  15  *              Alan Cox        :       verify_area() now used correctly
  16  *              Alan Cox        :       new skbuff lists, look ma no backlogs!
  17  *              Alan Cox        :       tidied skbuff lists.
  18  *              Alan Cox        :       Now uses generic datagram routines I
  19  *                                      added. Also fixed the peek/read crash
  20  *                                      from all old Linux datagram code.
  21  *              Alan Cox        :       Uses the improved datagram code.
  22  *              Alan Cox        :       Added NULL's for socket options.
  23  *              Alan Cox        :       Re-commented the code.
  24  *              Alan Cox        :       Use new kernel side addressing
  25  *              Rob Janssen     :       Correct MTU usage.
  26  *              Dave Platt      :       Counter leaks caused by incorrect
  27  *                                      interrupt locking and some slightly
  28  *                                      dubious gcc output. Can you read
  29  *                                      compiler: it said _VOLATILE_
  30  *      Richard Kooijman        :       Timestamp fixes.
  31  *              Alan Cox        :       New buffers. Use sk->mac.raw
  32  *
  33  *              This program is free software; you can redistribute it and/or
  34  *              modify it under the terms of the GNU General Public License
  35  *              as published by the Free Software Foundation; either version
  36  *              2 of the License, or (at your option) any later version.
  37  *
  38  */
  39  
  40 #include <linux/types.h>
  41 #include <linux/sched.h>
  42 #include <linux/mm.h>
  43 #include <linux/fcntl.h>
  44 #include <linux/socket.h>
  45 #include <linux/in.h>
  46 #include <linux/inet.h>
  47 #include <linux/netdevice.h>
  48 #include <net/ip.h>
  49 #include <net/protocol.h>
  50 #include <linux/skbuff.h>
  51 #include <net/sock.h>
  52 #include <linux/errno.h>
  53 #include <linux/timer.h>
  54 #include <asm/system.h>
  55 #include <asm/segment.h>
  56 
  57 /*
  58  *      We really ought to have a single public _inline_ min function!
  59  */
  60 
  61 static unsigned long min(unsigned long a, unsigned long b)
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  62 {
  63         if (a < b) 
  64                 return(a);
  65         return(b);
  66 }
  67 
  68 
  69 /*
  70  *      This should be the easiest of all, all we do is copy it into a buffer. 
  71  */
  72  
  73 int packet_rcv(struct sk_buff *skb, struct device *dev,  struct packet_type *pt)
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  74 {
  75         struct sock *sk;
  76         unsigned long flags;
  77         
  78         /*
  79          *      When we registered the protocol we saved the socket in the data
  80          *      field for just this event.
  81          */
  82 
  83         sk = (struct sock *) pt->data;  
  84         
  85         /*
  86          *      Yank back the headers
  87          */
  88          
  89         skb_push(skb,skb->data-skb->mac.raw);
  90 
  91         /*
  92          *      The SOCK_PACKET socket receives _all_ frames.
  93          */
  94          
  95         skb->dev = dev;
  96 
  97         /*
  98          *      Charge the memory to the socket. This is done specifically
  99          *      to prevent sockets using all the memory up.
 100          */
 101          
 102         if (sk->rmem_alloc & 0xFF000000) {
 103                 printk("packet_rcv: sk->rmem_alloc = %ld\n", sk->rmem_alloc);
 104                 sk->rmem_alloc = 0;
 105         }
 106 
 107         if (sk->rmem_alloc + skb->truesize >= sk->rcvbuf) 
 108         {
 109 /*              printk("packet_rcv: drop, %d+%d>%d\n", sk->rmem_alloc, skb->truesize, sk->rcvbuf); */
 110                 skb->sk = NULL;
 111                 kfree_skb(skb, FREE_READ);
 112                 return(0);
 113         }
 114 
 115         save_flags(flags);
 116         cli();
 117 
 118         skb->sk = sk;
 119         sk->rmem_alloc += skb->truesize;        
 120 
 121         /*
 122          *      Queue the packet up, and wake anyone waiting for it.
 123          */
 124 
 125         skb_queue_tail(&sk->receive_queue,skb);
 126         if(!sk->dead)
 127                 sk->data_ready(sk,skb->len);
 128                 
 129         restore_flags(flags);
 130 
 131         /*
 132          *      Processing complete.
 133          */
 134          
 135         return(0);
 136 }
 137 
 138 
 139 /*
 140  *      Output a raw packet to a device layer. This bypasses all the other
 141  *      protocol layers and you must therefore supply it with a complete frame
 142  */
 143  
 144 static int packet_sendto(struct sock *sk, unsigned char *from, int len,
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 145               int noblock, unsigned flags, struct sockaddr_in *usin,
 146               int addr_len)
 147 {
 148         struct sk_buff *skb;
 149         struct device *dev;
 150         struct sockaddr *saddr=(struct sockaddr *)usin;
 151 
 152         /*
 153          *      Check the flags. 
 154          */
 155 
 156         if (flags) 
 157                 return(-EINVAL);
 158 
 159         /*
 160          *      Get and verify the address. 
 161          */
 162          
 163         if (usin) 
 164         {
 165                 if (addr_len < sizeof(*saddr)) 
 166                         return(-EINVAL);
 167         } 
 168         else
 169                 return(-EINVAL);        /* SOCK_PACKET must be sent giving an address */
 170         
 171         /*
 172          *      Find the device first to size check it 
 173          */
 174 
 175         saddr->sa_data[13] = 0;
 176         dev = dev_get(saddr->sa_data);
 177         if (dev == NULL) 
 178         {
 179                 return(-ENXIO);
 180         }
 181         
 182         /*
 183          *      You may not queue a frame bigger than the mtu. This is the lowest level
 184          *      raw protocol and you must do your own fragmentation at this level.
 185          */
 186          
 187         if(len>dev->mtu+dev->hard_header_len)
 188                 return -EMSGSIZE;
 189 
 190         skb = sk->prot->wmalloc(sk, len, 0, GFP_KERNEL);
 191 
 192         /*
 193          *      If the write buffer is full, then tough. At this level the user gets to
 194          *      deal with the problem - do your own algorithmic backoffs.
 195          */
 196          
 197         if (skb == NULL) 
 198         {
 199                 return(-ENOBUFS);
 200         }
 201         
 202         /*
 203          *      Fill it in 
 204          */
 205          
 206         skb->sk = sk;
 207         skb->free = 1;
 208         memcpy_fromfs(skb_put(skb,len), from, len);
 209         skb->arp = 1;           /* No ARP needs doing on this (complete) frame */
 210 
 211         /*
 212          *      Now send it
 213          */
 214 
 215         if (dev->flags & IFF_UP) 
 216                 dev_queue_xmit(skb, dev, sk->priority);
 217         else
 218                 kfree_skb(skb, FREE_WRITE);
 219         return(len);
 220 }
 221 
 222 /*
 223  *      A write to a SOCK_PACKET can't actually do anything useful and will
 224  *      always fail but we include it for completeness and future expansion.
 225  */
 226 
 227 static int packet_write(struct sock *sk, unsigned char *buff, 
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 228              int len, int noblock,  unsigned flags)
 229 {
 230         return(packet_sendto(sk, buff, len, noblock, flags, NULL, 0));
 231 }
 232 
 233 /*
 234  *      Close a SOCK_PACKET socket. This is fairly simple. We immediately go
 235  *      to 'closed' state and remove our protocol entry in the device list.
 236  *      The release_sock() will destroy the socket if a user has closed the
 237  *      file side of the object.
 238  */
 239 
 240 static void packet_close(struct sock *sk, int timeout)
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 241 {
 242         sk->inuse = 1;
 243         sk->state = TCP_CLOSE;
 244         dev_remove_pack((struct packet_type *)sk->pair);
 245         kfree_s((void *)sk->pair, sizeof(struct packet_type));
 246         sk->pair = NULL;
 247         release_sock(sk);
 248 }
 249 
 250 /*
 251  *      Create a packet of type SOCK_PACKET. We do one slightly irregular
 252  *      thing here that wants tidying up. We borrow the 'pair' pointer in
 253  *      the socket object so we can find the packet_type entry in the
 254  *      device list. The reverse is easy as we use the data field of the
 255  *      packet type to point to our socket.
 256  */
 257 
 258 static int packet_init(struct sock *sk)
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 259 {
 260         struct packet_type *p;
 261 
 262         p = (struct packet_type *) kmalloc(sizeof(*p), GFP_KERNEL);
 263         if (p == NULL) 
 264                 return(-ENOMEM);
 265 
 266         p->func = packet_rcv;
 267         p->type = sk->num;
 268         p->data = (void *)sk;
 269         p->dev = NULL;
 270         dev_add_pack(p);
 271    
 272         /*
 273          *      We need to remember this somewhere. 
 274          */
 275    
 276         sk->pair = (struct sock *)p;
 277 
 278         return(0);
 279 }
 280 
 281 
 282 /*
 283  *      Pull a packet from our receive queue and hand it to the user.
 284  *      If necessary we block.
 285  */
 286  
 287 int packet_recvfrom(struct sock *sk, unsigned char *to, int len,
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 288                 int noblock, unsigned flags, struct sockaddr_in *sin,
 289                 int *addr_len)
 290 {
 291         int copied=0;
 292         struct sk_buff *skb;
 293         struct sockaddr *saddr;
 294         int err;
 295 
 296         saddr = (struct sockaddr *)sin;
 297 
 298         if (sk->shutdown & RCV_SHUTDOWN) 
 299                 return(0);
 300                 
 301         /*
 302          *      If the address length field is there to be filled in, we fill
 303          *      it in now.
 304          */
 305 
 306         if (addr_len) 
 307                 *addr_len=sizeof(*saddr);
 308         
 309         /*
 310          *      Call the generic datagram receiver. This handles all sorts
 311          *      of horrible races and re-entrancy so we can forget about it
 312          *      in the protocol layers.
 313          */
 314          
 315         skb=skb_recv_datagram(sk,flags,noblock,&err);
 316         
 317         /*
 318          *      An error occurred so return it. Because skb_recv_datagram() 
 319          *      handles the blocking we don't see and worry about blocking
 320          *      retries.
 321          */
 322          
 323         if(skb==NULL)
 324                 return err;
 325                 
 326         /*
 327          *      You lose any data beyond the buffer you gave. If it worries a
 328          *      user program they can ask the device for its MTU anyway.
 329          */
 330          
 331         copied = min(len, skb->len);
 332 
 333         memcpy_tofs(to, skb->data, copied);     /* We can't use skb_copy_datagram here */
 334         sk->stamp=skb->stamp;
 335 
 336         /*
 337          *      Copy the address. 
 338          */
 339          
 340         if (saddr) 
 341         {
 342                 saddr->sa_family = skb->dev->type;
 343                 memcpy(saddr->sa_data,skb->dev->name, 14);
 344         }
 345         
 346         /*
 347          *      Free or return the buffer as appropriate. Again this hides all the
 348          *      races and re-entrancy issues from us.
 349          */
 350 
 351         skb_free_datagram(skb);
 352 
 353         /*
 354          *      We are done.
 355          */
 356          
 357         release_sock(sk);
 358         return(copied);
 359 }
 360 
 361 
 362 /*
 363  *      A packet read can succeed and is just the same as a recvfrom but without the
 364  *      addresses being recorded.
 365  */
 366 
 367 int packet_read(struct sock *sk, unsigned char *buff,
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 368             int len, int noblock, unsigned flags)
 369 {
 370         return(packet_recvfrom(sk, buff, len, noblock, flags, NULL, NULL));
 371 }
 372 
 373 
 374 /*
 375  *      This structure declares to the lower layer socket subsystem currently
 376  *      incorrectly embedded in the IP code how to behave. This interface needs
 377  *      a lot of work and will change.
 378  */
 379  
 380 struct proto packet_prot = 
 381 {
 382         sock_wmalloc,
 383         sock_rmalloc,
 384         sock_wfree,
 385         sock_rfree,
 386         sock_rspace,
 387         sock_wspace,
 388         packet_close,
 389         packet_read,
 390         packet_write,
 391         packet_sendto,
 392         packet_recvfrom,
 393         ip_build_header,        /* Not actually used */
 394         NULL,
 395         NULL,
 396         ip_queue_xmit,          /* These two are not actually used */
 397         NULL,
 398         NULL,
 399         NULL,
 400         NULL, 
 401         datagram_select,
 402         NULL,
 403         packet_init,
 404         NULL,
 405         NULL,                   /* No set/get socket options */
 406         NULL,
 407         128,
 408         0,
 409         "PACKET",
 410         0, 0
 411 };

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