root/net/core/datagram.c

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

DEFINITIONS

This source file includes following definitions.
  1. skb_recv_datagram
  2. skb_free_datagram
  3. skb_copy_datagram
  4. skb_copy_datagram_iovec
  5. datagram_select

   1 /*
   2  *      SUCS NET3:
   3  *
   4  *      Generic datagram handling routines. These are generic for all protocols. Possibly a generic IP version on top
   5  *      of these would make sense. Not tonight however 8-).
   6  *      This is used because UDP, RAW, PACKET, DDP, IPX, AX.25 and NetROM layer all have identical select code and mostly
   7  *      identical recvmsg() code. So we share it here. The select was shared before but buried in udp.c so I moved it.
   8  *
   9  *      Authors:        Alan Cox <alan@cymru.net>. (datagram_select() from old udp.c code)
  10  *
  11  *      Fixes:
  12  *              Alan Cox        :       NULL return from skb_peek_copy() understood
  13  *              Alan Cox        :       Rewrote skb_read_datagram to avoid the skb_peek_copy stuff.
  14  *              Alan Cox        :       Added support for SOCK_SEQPACKET. IPX can no longer use the SO_TYPE hack but
  15  *                                      AX.25 now works right, and SPX is feasible.
  16  *              Alan Cox        :       Fixed write select of non IP protocol crash.
  17  *              Florian  La Roche:      Changed for my new skbuff handling.
  18  *              Darryl Miles    :       Fixed non-blocking SOCK_SEQPACKET.
  19  *              Linus Torvalds  :       BSD semantic fixes.
  20  *              Alan Cox        :       Datagram iovec handling
  21  *
  22  */
  23 
  24 #include <linux/types.h>
  25 #include <linux/kernel.h>
  26 #include <asm/segment.h>
  27 #include <asm/system.h>
  28 #include <linux/mm.h>
  29 #include <linux/interrupt.h>
  30 #include <linux/in.h>
  31 #include <linux/errno.h>
  32 #include <linux/sched.h>
  33 #include <linux/inet.h>
  34 #include <linux/netdevice.h>
  35 #include <net/ip.h>
  36 #include <net/protocol.h>
  37 #include <net/route.h>
  38 #include <net/tcp.h>
  39 #include <net/udp.h>
  40 #include <linux/skbuff.h>
  41 #include <net/sock.h>
  42 
  43 
  44 /*
  45  *      Get a datagram skbuff, understands the peeking, nonblocking wakeups and possible
  46  *      races. This replaces identical code in packet,raw and udp, as well as the IPX
  47  *      AX.25 and Appletalk. It also finally fixes the long standing peek and read
  48  *      race for datagram sockets. If you alter this routine remember it must be
  49  *      re-entrant.
  50  */
  51 
  52 struct sk_buff *skb_recv_datagram(struct sock *sk, unsigned flags, int noblock, int *err)
     /* [previous][next][first][last][top][bottom][index][help] */
  53 {
  54         struct sk_buff *skb;
  55         unsigned long intflags;
  56 
  57         /* Socket is inuse - so the timer doesn't attack it */
  58         save_flags(intflags);
  59 restart:
  60         sk->inuse = 1;
  61         while(skb_peek(&sk->receive_queue) == NULL)     /* No data */
  62         {
  63                 /* If we are shutdown then no more data is going to appear. We are done */
  64                 if (sk->shutdown & RCV_SHUTDOWN)
  65                 {
  66                         release_sock(sk);
  67                         *err=0;
  68                         return NULL;
  69                 }
  70 
  71                 if(sk->err)
  72                 {
  73                         release_sock(sk);
  74                         *err=sock_error(sk);
  75                         restore_flags(intflags);
  76                         return NULL;
  77                 }
  78 
  79                 /* Sequenced packets can come disconnected. If so we report the problem */
  80                 if(sk->type==SOCK_SEQPACKET && sk->state!=TCP_ESTABLISHED)
  81                 {
  82                         release_sock(sk);
  83                         *err=-ENOTCONN;
  84                         return NULL;
  85                 }
  86 
  87                 /* User doesn't want to wait */
  88                 if (noblock)
  89                 {
  90                         release_sock(sk);
  91                         *err=-EAGAIN;
  92                         return NULL;
  93                 }
  94                 release_sock(sk);
  95 
  96                 /* Interrupts off so that no packet arrives before we begin sleeping.
  97                    Otherwise we might miss our wake up */
  98                 cli();
  99                 if (skb_peek(&sk->receive_queue) == NULL)
 100                 {
 101                         interruptible_sleep_on(sk->sleep);
 102                         /* Signals may need a restart of the syscall */
 103                         if (current->signal & ~current->blocked)
 104                         {
 105                                 restore_flags(intflags);;
 106                                 *err=-ERESTARTSYS;
 107                                 return(NULL);
 108                         }
 109                         if(sk->err != 0)        /* Error while waiting for packet
 110                                                    eg an icmp sent earlier by the
 111                                                    peer has finally turned up now */
 112                         {
 113                                 *err = sock_error(sk);
 114                                 restore_flags(intflags);
 115                                 return NULL;
 116                         }
 117                 }
 118                 sk->inuse = 1;
 119                 restore_flags(intflags);
 120           }
 121           /* Again only user level code calls this function, so nothing interrupt level
 122              will suddenly eat the receive_queue */
 123           if (!(flags & MSG_PEEK))
 124           {
 125                 skb=skb_dequeue(&sk->receive_queue);
 126                 if(skb!=NULL)
 127                         skb->users++;
 128                 else
 129                         goto restart;   /* Avoid race if someone beats us to the data */
 130           }
 131           else
 132           {
 133                 cli();
 134                 skb=skb_peek(&sk->receive_queue);
 135                 if(skb!=NULL)
 136                         skb->users++;
 137                 restore_flags(intflags);
 138                 if(skb==NULL)   /* shouldn't happen but .. */
 139                         *err=-EAGAIN;
 140           }
 141           return skb;
 142 }
 143 
 144 void skb_free_datagram(struct sk_buff *skb)
     /* [previous][next][first][last][top][bottom][index][help] */
 145 {
 146         unsigned long flags;
 147 
 148         save_flags(flags);
 149         cli();
 150         skb->users--;
 151         if(skb->users>0)
 152         {
 153                 restore_flags(flags);
 154                 return;
 155         }
 156         /* See if it needs destroying */
 157         if(!skb->next && !skb->prev)    /* Been dequeued by someone - ie it's read */
 158                 kfree_skb(skb,FREE_READ);
 159         restore_flags(flags);
 160 }
 161 
 162 /*
 163  *      Copy a datagram to a linear buffer.
 164  */
 165 
 166 void skb_copy_datagram(struct sk_buff *skb, int offset, char *to, int size)
     /* [previous][next][first][last][top][bottom][index][help] */
 167 {
 168         memcpy_tofs(to,skb->h.raw+offset,size);
 169 }
 170 
 171 
 172 /*
 173  *      Copy a datagram to an iovec.
 174  */
 175  
 176 void skb_copy_datagram_iovec(struct sk_buff *skb, int offset, struct iovec *to, int size)
     /* [previous][next][first][last][top][bottom][index][help] */
 177 {
 178         memcpy_toiovec(to,skb->h.raw+offset,size);
 179 }
 180 
 181 /*
 182  *      Datagram select: Again totally generic. Moved from udp.c
 183  *      Now does seqpacket.
 184  */
 185 
 186 int datagram_select(struct sock *sk, int sel_type, select_table *wait)
     /* [previous][next][first][last][top][bottom][index][help] */
 187 {
 188         select_wait(sk->sleep, wait);
 189         switch(sel_type)
 190         {
 191                 case SEL_IN:
 192                         if (sk->err)
 193                                 return 1;
 194                         if (sk->shutdown & RCV_SHUTDOWN)
 195                                 return 1;
 196                         if (sk->type==SOCK_SEQPACKET && sk->state==TCP_CLOSE)
 197                         {
 198                                 /* Connection closed: Wake up */
 199                                 return(1);
 200                         }
 201                         if (skb_peek(&sk->receive_queue) != NULL)
 202                         {       /* This appears to be consistent
 203                                    with other stacks */
 204                                 return(1);
 205                         }
 206                         return(0);
 207 
 208                 case SEL_OUT:
 209                         if (sk->err)
 210                                 return 1;
 211                         if (sk->shutdown & SEND_SHUTDOWN)
 212                                 return 1;
 213                         if (sk->type==SOCK_SEQPACKET && sk->state==TCP_SYN_SENT)
 214                         {
 215                                 /* Connection still in progress */
 216                                 break;
 217                         }
 218                         if (sk->prot && sock_wspace(sk) >= MIN_WRITE_SPACE)
 219                         {
 220                                 return(1);
 221                         }
 222                         if (sk->prot==NULL && sk->sndbuf-sk->wmem_alloc >= MIN_WRITE_SPACE)
 223                         {
 224                                 return(1);
 225                         }
 226                         return(0);
 227 
 228                 case SEL_EX:
 229                         if (sk->err)
 230                                 return(1); /* Socket has gone into error state (eg icmp error) */
 231                         return(0);
 232         }
 233         return(0);
 234 }

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