net/inet/datagram.c

/* */
This source file includes following definitions.
skb_recv_datagram
skb_free_datagram
skb_copy_datagram
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 and the to be released IPX layer all have identical select code and mostly
   7  *      identical recvfrom() 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 <iiitac@pyr.swan.ac.uk>. (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  *
  19  *      Note:
  20  *              A lot of this will change when the protocol/socket separation
  21  *      occurs. Using this will make things reasonably clean.
  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 "ip.h"
  36 #include "protocol.h"
  37 #include "route.h"
  38 #include "tcp.h"
  39 #include "udp.h"
  40 #include <linux/skbuff.h>
  41 #include "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 yet to
  47  *      be released IPX support. 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)
     /*  */
  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=-sk->err;
  75                         sk->err=0;
  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 = -sk->err;
 114                                 sk->err=0;
 115                                 restore_flags(intflags);
 116                                 return NULL;
 117                         }
 118                 }
 119                 sk->inuse = 1;
 120                 restore_flags(intflags);
 121           }
 122           /* Again only user level code calls this function, so nothing interrupt level
 123              will suddenly eat the receive_queue */
 124           if (!(flags & MSG_PEEK))
 125           {
 126                 skb=skb_dequeue(&sk->receive_queue);
 127                 if(skb!=NULL)
 128                         skb->users++;
 129                 else
 130                         goto restart;   /* Avoid race if someone beats us to the data */
 131           }
 132           else
 133           {
 134                 cli();
 135                 skb=skb_peek(&sk->receive_queue);
 136                 if(skb!=NULL)
 137                         skb->users++;
 138                 restore_flags(intflags);
 139                 if(skb==NULL)   /* shouldn't happen but .. */
 140                         *err=-EAGAIN;
 141           }
 142           return skb;
 143 }
 144 
 145 void skb_free_datagram(struct sk_buff *skb)
     /*  */
 146 {
 147         unsigned long flags;
 148 
 149         save_flags(flags);
 150         cli();
 151         skb->users--;
 152         if(skb->users>0)
 153         {
 154                 restore_flags(flags);
 155                 return;
 156         }
 157         /* See if it needs destroying */
 158         if(!skb->next && !skb->prev)    /* Been dequeued by someone - ie it's read */
 159                 kfree_skb(skb,FREE_READ);
 160         restore_flags(flags);
 161 }
 162 
 163 void skb_copy_datagram(struct sk_buff *skb, int offset, char *to, int size)
     /*  */
 164 {
 165         /* We will know all about the fraglist options to allow >4K receives
 166            but not this release */
 167         memcpy_tofs(to,skb->h.raw+offset,size);
 168 }
 169 
 170 /*
 171  *      Datagram select: Again totally generic. Moved from udp.c
 172  *      Now does seqpacket.
 173  */
 174 
 175 int datagram_select(struct sock *sk, int sel_type, select_table *wait)
     /*  */
 176 {
 177         select_wait(sk->sleep, wait);
 178         switch(sel_type)
 179         {
 180                 case SEL_IN:
 181                         if (sk->type==SOCK_SEQPACKET && sk->state==TCP_CLOSE)
 182                         {
 183                                 /* Connection closed: Wake up */
 184                                 return(1);
 185                         }
 186                         if (skb_peek(&sk->receive_queue) != NULL || sk->err != 0)
 187                         {       /* This appears to be consistent
 188                                    with other stacks */
 189                                 return(1);
 190                         }
 191                         return(0);
 192 
 193                 case SEL_OUT:
 194                         if (sk->prot && sk->prot->wspace(sk) >= MIN_WRITE_SPACE)
 195                         {
 196                                 return(1);
 197                         }
 198                         if (sk->prot==NULL && sk->sndbuf-sk->wmem_alloc >= MIN_WRITE_SPACE)
 199                         {
 200                                 return(1);
 201                         }
 202                         return(0);
 203 
 204                 case SEL_EX:
 205                         if (sk->err)
 206                                 return(1); /* Socket has gone into error state (eg icmp error) */
 207                         return(0);
 208         }
 209         return(0);
 210 }
/* */
root/net/inet/datagram.c

DEFINITIONS
