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*/
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/config.h>
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 "ip.h"
37 #include "protocol.h"
38 #include "route.h"
39 #include "tcp.h"
40 #include "udp.h"
41 #include <linux/skbuff.h>
42 #include "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 yet to
48 * be released IPX support. 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)
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*/
54 {
55 struct sk_buff *skb;
56
57 /* Socket is inuse - so the timer doesn't attack it */
58 restart:
59 sk->inuse = 1;
60 while(skb_peek(&sk->receive_queue) == NULL) /* No data */
61 {
62 /* If we are shutdown then no more data is going to appear. We are done */
63 if (sk->shutdown & RCV_SHUTDOWN)
64 {
65 release_sock(sk);
66 *err=0;
67 return NULL;
68 }
69
70 if(sk->err)
71 {
72 release_sock(sk);
73 *err=-sk->err;
74 sk->err=0;
75 return NULL;
76 }
77
78 /* Sequenced packets can come disconnected. If so we report the problem */
79 if(sk->type==SOCK_SEQPACKET && sk->state!=TCP_ESTABLISHED)
80 {
81 release_sock(sk);
82 *err=-ENOTCONN;
83 return NULL;
84 }
85
86 /* User doesn't want to wait */
87 if (noblock)
88 {
89 release_sock(sk);
90 *err=-EAGAIN;
91 return NULL;
92 }
93 release_sock(sk);
94
95 /* Interrupts off so that no packet arrives before we begin sleeping.
96 Otherwise we might miss our wake up */
97 cli();
98 if (skb_peek(&sk->receive_queue) == NULL)
99 {
100 interruptible_sleep_on(sk->sleep);
101 /* Signals may need a restart of the syscall */
102 if (current->signal & ~current->blocked)
103 {
104 sti();
105 *err=-ERESTARTSYS;
106 return(NULL);
107 }
108 if(sk->err != 0) /* Error while waiting for packet
109 eg an icmp sent earlier by the
110 peer has finally turned up now */
111 {
112 *err = -sk->err;
113 sti();
114 sk->err=0;
115 return NULL;
116 }
117 }
118 sk->inuse = 1;
119 sti();
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 sti();
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)
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*/
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 its read */
158 kfree_skb(skb,FREE_READ);
159 restore_flags(flags);
160 }
161
162 void skb_copy_datagram(struct sk_buff *skb, int offset, char *to, int size)
/* */
163 {
164 /* We will know all about the fraglist options to allow >4K receives
165 but not this release */
166 memcpy_tofs(to,skb->h.raw+offset,size);
167 }
168
169 /*
170 * Datagram select: Again totally generic. Moved from udp.c
171 * Now does seqpacket.
172 */
173
174 int datagram_select(struct sock *sk, int sel_type, select_table *wait)
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*/
175 {
176 select_wait(sk->sleep, wait);
177 switch(sel_type)
178 {
179 case SEL_IN:
180 if (sk->type==SOCK_SEQPACKET && sk->state==TCP_CLOSE)
181 {
182 /* Connection closed: Wake up */
183 return(1);
184 }
185 if (skb_peek(&sk->receive_queue) != NULL || sk->err != 0)
186 { /* This appears to be consistent
187 with other stacks */
188 return(1);
189 }
190 return(0);
191
192 case SEL_OUT:
193 if (sk->prot && sk->prot->wspace(sk) >= MIN_WRITE_SPACE)
194 {
195 return(1);
196 }
197 if (sk->prot==NULL && sk->sndbuf-sk->wmem_alloc >= MIN_WRITE_SPACE)
198 {
199 return(1);
200 }
201 return(0);
202
203 case SEL_EX:
204 if (sk->err)
205 return(1); /* Socket has gone into error state (eg icmp error) */
206 return(0);
207 }
208 return(0);
209 }
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*/