net/core/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  *              Darryl Miles    :       Fixed non-blocking SOCK_SEQPACKET.
  19  *
  20  *      Note:
  21  *              A lot of this will change when the protocol/socket separation
  22  *      occurs. Using this will make things reasonably clean.
  23  */
  24 
  25 #include <linux/types.h>
  26 #include <linux/kernel.h>
  27 #include <asm/segment.h>
  28 #include <asm/system.h>
  29 #include <linux/mm.h>
  30 #include <linux/interrupt.h>
  31 #include <linux/in.h>
  32 #include <linux/errno.h>
  33 #include <linux/sched.h>
  34 #include <linux/inet.h>
  35 #include <linux/netdevice.h>
  36 #include <net/ip.h>
  37 #include <net/protocol.h>
  38 #include <net/route.h>
  39 #include <net/tcp.h>
  40 #include <net/udp.h>
  41 #include <linux/skbuff.h>
  42 #include <net/sock.h>
  43 
  44 
  45 /*
  46  *      Get a datagram skbuff, understands the peeking, nonblocking wakeups and possible
  47  *      races. This replaces identical code in packet,raw and udp, as well as the IPX
  48  *      AX.25 and Appletalk. It also finally fixes the long standing peek and read
  49  *      race for datagram sockets. If you alter this routine remember it must be
  50  *      re-entrant.
  51  */
  52 
  53 struct sk_buff *skb_recv_datagram(struct sock *sk, unsigned flags, int noblock, int *err)
     /*  */
  54 {
  55         struct sk_buff *skb;
  56         unsigned long intflags;
  57 
  58         /* Socket is inuse - so the timer doesn't attack it */
  59         save_flags(intflags);
  60 restart:
  61         sk->inuse = 1;
  62         while(skb_peek(&sk->receive_queue) == NULL)     /* No data */
  63         {
  64                 /* If we are shutdown then no more data is going to appear. We are done */
  65                 if (sk->shutdown & RCV_SHUTDOWN)
  66                 {
  67                         release_sock(sk);
  68                         *err=0;
  69                         return NULL;
  70                 }
  71 
  72                 if(sk->err)
  73                 {
  74                         release_sock(sk);
  75                         cli();
  76                         *err=-sk->err;
  77                         sk->err=0;
  78                         restore_flags(intflags);
  79                         return NULL;
  80                 }
  81 
  82                 /* Sequenced packets can come disconnected. If so we report the problem */
  83                 if(sk->type==SOCK_SEQPACKET && sk->state!=TCP_ESTABLISHED)
  84                 {
  85                         release_sock(sk);
  86                         *err=-ENOTCONN;
  87                         return NULL;
  88                 }
  89 
  90                 /* User doesn't want to wait */
  91                 if (noblock)
  92                 {
  93                         release_sock(sk);
  94                         *err=-EAGAIN;
  95                         return NULL;
  96                 }
  97                 release_sock(sk);
  98 
  99                 /* Interrupts off so that no packet arrives before we begin sleeping.
 100                    Otherwise we might miss our wake up */
 101                 cli();
 102                 if (skb_peek(&sk->receive_queue) == NULL)
 103                 {
 104                         interruptible_sleep_on(sk->sleep);
 105                         /* Signals may need a restart of the syscall */
 106                         if (current->signal & ~current->blocked)
 107                         {
 108                                 restore_flags(intflags);;
 109                                 *err=-ERESTARTSYS;
 110                                 return(NULL);
 111                         }
 112                         if(sk->err != 0)        /* Error while waiting for packet
 113                                                    eg an icmp sent earlier by the
 114                                                    peer has finally turned up now */
 115                         {
 116                                 *err = -sk->err;
 117                                 sk->err=0;
 118                                 restore_flags(intflags);
 119                                 return NULL;
 120                         }
 121                 }
 122                 sk->inuse = 1;
 123                 restore_flags(intflags);
 124           }
 125           /* Again only user level code calls this function, so nothing interrupt level
 126              will suddenly eat the receive_queue */
 127           if (!(flags & MSG_PEEK))
 128           {
 129                 skb=skb_dequeue(&sk->receive_queue);
 130                 if(skb!=NULL)
 131                         skb->users++;
 132                 else
 133                         goto restart;   /* Avoid race if someone beats us to the data */
 134           }
 135           else
 136           {
 137                 cli();
 138                 skb=skb_peek(&sk->receive_queue);
 139                 if(skb!=NULL)
 140                         skb->users++;
 141                 restore_flags(intflags);
 142                 if(skb==NULL)   /* shouldn't happen but .. */
 143                         *err=-EAGAIN;
 144           }
 145           return skb;
 146 }
 147 
 148 void skb_free_datagram(struct sk_buff *skb)
     /*  */
 149 {
 150         unsigned long flags;
 151 
 152         save_flags(flags);
 153         cli();
 154         skb->users--;
 155         if(skb->users>0)
 156         {
 157                 restore_flags(flags);
 158                 return;
 159         }
 160         /* See if it needs destroying */
 161         if(!skb->next && !skb->prev)    /* Been dequeued by someone - ie it's read */
 162                 kfree_skb(skb,FREE_READ);
 163         restore_flags(flags);
 164 }
 165 
 166 void skb_copy_datagram(struct sk_buff *skb, int offset, char *to, int size)
     /*  */
 167 {
 168         memcpy_tofs(to,skb->h.raw+offset,size);
 169 }
 170 
 171 /*
 172  *      Datagram select: Again totally generic. Moved from udp.c
 173  *      Now does seqpacket.
 174  */
 175 
 176 int datagram_select(struct sock *sk, int sel_type, select_table *wait)
     /*  */
 177 {
 178         select_wait(sk->sleep, wait);
 179         switch(sel_type)
 180         {
 181                 case SEL_IN:
 182                         if (sk->type==SOCK_SEQPACKET && sk->state==TCP_CLOSE)
 183                         {
 184                                 /* Connection closed: Wake up */
 185                                 return(1);
 186                         }
 187                         if (skb_peek(&sk->receive_queue) != NULL || sk->err != 0)
 188                         {       /* This appears to be consistent
 189                                    with other stacks */
 190                                 return(1);
 191                         }
 192                         return(0);
 193 
 194                 case SEL_OUT:
 195                         if (sk->type==SOCK_SEQPACKET && sk->state==TCP_SYN_SENT)
 196                         {
 197                                 /* Connection still in progress */
 198                                 return(0);
 199                         }
 200                         if (sk->prot && sk->prot->wspace(sk) >= MIN_WRITE_SPACE)
 201                         {
 202                                 return(1);
 203                         }
 204                         if (sk->prot==NULL && sk->sndbuf-sk->wmem_alloc >= MIN_WRITE_SPACE)
 205                         {
 206                                 return(1);
 207                         }
 208                         return(0);
 209 
 210                 case SEL_EX:
 211                         if (sk->err)
 212                                 return(1); /* Socket has gone into error state (eg icmp error) */
 213                         return(0);
 214         }
 215         return(0);
 216 }
/* */
root/net/core/datagram.c

DEFINITIONS
