root/net/core/datagram.c

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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 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  *              Linus Torvalds  :       BSD semantic fixes.
  20  *              Alan Cox        :       Datagram iovec handling
  21  *
  22  *      Note:
  23  *              A lot of this will change when the protocol/socket separation
  24  *      occurs. Using this will make things reasonably clean.
  25  */
  26 
  27 #include <linux/types.h>
  28 #include <linux/kernel.h>
  29 #include <asm/segment.h>
  30 #include <asm/system.h>
  31 #include <linux/mm.h>
  32 #include <linux/interrupt.h>
  33 #include <linux/in.h>
  34 #include <linux/errno.h>
  35 #include <linux/sched.h>
  36 #include <linux/inet.h>
  37 #include <linux/netdevice.h>
  38 #include <net/ip.h>
  39 #include <net/protocol.h>
  40 #include <net/route.h>
  41 #include <net/tcp.h>
  42 #include <net/udp.h>
  43 #include <linux/skbuff.h>
  44 #include <net/sock.h>
  45 
  46 
  47 /*
  48  *      Get a datagram skbuff, understands the peeking, nonblocking wakeups and possible
  49  *      races. This replaces identical code in packet,raw and udp, as well as the IPX
  50  *      AX.25 and Appletalk. It also finally fixes the long standing peek and read
  51  *      race for datagram sockets. If you alter this routine remember it must be
  52  *      re-entrant.
  53  */
  54 
  55 struct sk_buff *skb_recv_datagram(struct sock *sk, unsigned flags, int noblock, int *err)
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  56 {
  57         struct sk_buff *skb;
  58         unsigned long intflags;
  59 
  60         /* Socket is inuse - so the timer doesn't attack it */
  61         save_flags(intflags);
  62 restart:
  63         sk->inuse = 1;
  64         while(skb_peek(&sk->receive_queue) == NULL)     /* No data */
  65         {
  66                 /* If we are shutdown then no more data is going to appear. We are done */
  67                 if (sk->shutdown & RCV_SHUTDOWN)
  68                 {
  69                         release_sock(sk);
  70                         *err=0;
  71                         return NULL;
  72                 }
  73 
  74                 if(sk->err)
  75                 {
  76                         release_sock(sk);
  77                         *err=sock_error(sk);
  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 = sock_error(sk);
 117                                 restore_flags(intflags);
 118                                 return NULL;
 119                         }
 120                 }
 121                 sk->inuse = 1;
 122                 restore_flags(intflags);
 123           }
 124           /* Again only user level code calls this function, so nothing interrupt level
 125              will suddenly eat the receive_queue */
 126           if (!(flags & MSG_PEEK))
 127           {
 128                 skb=skb_dequeue(&sk->receive_queue);
 129                 if(skb!=NULL)
 130                         skb->users++;
 131                 else
 132                         goto restart;   /* Avoid race if someone beats us to the data */
 133           }
 134           else
 135           {
 136                 cli();
 137                 skb=skb_peek(&sk->receive_queue);
 138                 if(skb!=NULL)
 139                         skb->users++;
 140                 restore_flags(intflags);
 141                 if(skb==NULL)   /* shouldn't happen but .. */
 142                         *err=-EAGAIN;
 143           }
 144           return skb;
 145 }
 146 
 147 void skb_free_datagram(struct sk_buff *skb)
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 148 {
 149         unsigned long flags;
 150 
 151         save_flags(flags);
 152         cli();
 153         skb->users--;
 154         if(skb->users>0)
 155         {
 156                 restore_flags(flags);
 157                 return;
 158         }
 159         /* See if it needs destroying */
 160         if(!skb->next && !skb->prev)    /* Been dequeued by someone - ie it's read */
 161                 kfree_skb(skb,FREE_READ);
 162         restore_flags(flags);
 163 }
 164 
 165 /*
 166  *      Copy a datagram to a linear buffer.
 167  */
 168 
 169 void skb_copy_datagram(struct sk_buff *skb, int offset, char *to, int size)
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 170 {
 171         memcpy_tofs(to,skb->h.raw+offset,size);
 172 }
 173 
 174 
 175 /*
 176  *      Copy a datagram to an iovec.
 177  */
 178  
 179 void skb_copy_datagram_iovec(struct sk_buff *skb, int offset, struct iovec *to, int size)
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 180 {
 181         memcpy_toiovec(to,skb->h.raw+offset,size);
 182 }
 183 
 184 /*
 185  *      Datagram select: Again totally generic. Moved from udp.c
 186  *      Now does seqpacket.
 187  */
 188 
 189 int datagram_select(struct sock *sk, int sel_type, select_table *wait)
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 190 {
 191         select_wait(sk->sleep, wait);
 192         switch(sel_type)
 193         {
 194                 case SEL_IN:
 195                         if (sk->err)
 196                                 return 1;
 197                         if (sk->shutdown & RCV_SHUTDOWN)
 198                                 return 1;
 199                         if (sk->type==SOCK_SEQPACKET && sk->state==TCP_CLOSE)
 200                         {
 201                                 /* Connection closed: Wake up */
 202                                 return(1);
 203                         }
 204                         if (skb_peek(&sk->receive_queue) != NULL)
 205                         {       /* This appears to be consistent
 206                                    with other stacks */
 207                                 return(1);
 208                         }
 209                         return(0);
 210 
 211                 case SEL_OUT:
 212                         if (sk->err)
 213                                 return 1;
 214                         if (sk->shutdown & SEND_SHUTDOWN)
 215                                 return 1;
 216                         if (sk->type==SOCK_SEQPACKET && sk->state==TCP_SYN_SENT)
 217                         {
 218                                 /* Connection still in progress */
 219                                 break;
 220                         }
 221                         if (sk->prot && sock_wspace(sk) >= MIN_WRITE_SPACE)
 222                         {
 223                                 return(1);
 224                         }
 225                         if (sk->prot==NULL && sk->sndbuf-sk->wmem_alloc >= MIN_WRITE_SPACE)
 226                         {
 227                                 return(1);
 228                         }
 229                         return(0);
 230 
 231                 case SEL_EX:
 232                         if (sk->err)
 233                                 return(1); /* Socket has gone into error state (eg icmp error) */
 234                         return(0);
 235         }
 236         return(0);
 237 }

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