udp.c

An implementation of the TCP/IP protocol suite for the LINUX operating system. INET is implemented u

  1 /*
  2  * INET         An implementation of the TCP/IP protocol suite for the LINUX
  3  *              operating system.  INET is implemented using the  BSD Socket
  4  *              interface as the means of communication with the user level.
  5  *
  6  *              The User Datagram Protocol (UDP).
  7  *
  8  * Version:     @(#)udp.c       1.0.13  06/02/93
  9  *
 10  * Authors:     Ross Biro, <[e-mail]>
 11  *              Fred N. van Kempen, <[e-mail]>
 12  *
 13  * Fixes:
 14  *              Alan Cox        :       verify_area() calls
 15  *              Alan Cox        :       stopped close while in use off icmp
 16  *                                      messages. Not a fix but a botch that
 17  *                                      for udp at least is 'valid'.
 18  *              Alan Cox        :       Fixed icmp handling properly
 19  *              Alan Cox        :       Correct error for oversized datagrams
 20  *              Alan Cox        :       Tidied select() semantics. 
 21  *              Alan Cox        :       udp_err() fixed properly, also now 
 22  *                                      select and read wake correctly on errors
 23  *              Alan Cox        :       udp_send verify_area moved to avoid mem leak
 24  *              Alan Cox        :       UDP can count its memory
 25  *              Alan Cox        :       send to an uknown connection causes
 26  *                                      an ECONNREFUSED off the icmp, but
 27  *                                      does NOT close.
 28  *              Alan Cox        :       Switched to new sk_buff handlers. No more backlog!
 29  *              Alan Cox        :       Using generic datagram code. Even smaller and the PEEK
 30  *                                      bug no longer crashes it.
 31  *              Fred Van Kempen :       Net2e support for sk->broadcast.
 32  *              Alan Cox        :       Uses skb_free_datagram
 33  *              Alan Cox        :       Added get/set sockopt support.
 34  *              Alan Cox        :       Broadcasting without option set returns EACCES.
 35  *              Alan Cox        :       No wakeup calls. Instead we now use the callbacks.
 36  *              Alan Cox        :       Use ip_tos and ip_ttl
 37  *
 38  *
 39  *              This program is free software; you can redistribute it and/or
 40  *              modify it under the terms of the GNU General Public License
 41  *              as published by the Free Software Foundation; either version
 42  *              2 of the License, or (at your option) any later version.
 43  */
 44  
 45 #include <asm/system.h>
 46 #include <asm/segment.h>
 47 #include <linux/types.h>
 48 #include <linux/sched.h>
 49 #include <linux/fcntl.h>
 50 #include <linux/socket.h>
 51 #include <linux/sockios.h>
 52 #include <linux/in.h>
 53 #include <linux/errno.h>
 54 #include <linux/timer.h>
 55 #include <linux/termios.h>
 56 #include <linux/mm.h>
 57 #include "inet.h"
 58 #include "dev.h"
 59 #include "ip.h"
 60 #include "protocol.h"
 61 #include "tcp.h"
 62 #include "skbuff.h"
 63 #include "sock.h"
 64 #include "udp.h"
 65 #include "icmp.h"
 66 
 67 
 68 #define min(a,b)        ((a)<(b)?(a):(b))
 69 
 70 
 71 static void
 72 print_udp(struct udphdr *uh)
 73 {
 74   if (inet_debug != DBG_UDP) return;
 75 
 76   if (uh == NULL) {
 77         printk("(NULL)\n");
 78         return;
 79   }
 80   printk("UDP: source = %d, dest = %d\n", ntohs(uh->source), ntohs(uh->dest));
 81   printk("     len = %d, check = %d\n", ntohs(uh->len), ntohs(uh->check));
 82 }
 83 
 84 
 85 /*
 86  * This routine is called by the ICMP module when it gets some
 87  * sort of error condition.  If err < 0 then the socket should
 88  * be closed and the error returned to the user.  If err > 0
 89  * it's just the icmp type << 8 | icmp code.  
 90  * Header points to the ip header of the error packet. We move
 91  * on past this. Then (as it used to claim before adjustment)
 92  * header points to the first 8 bytes of the udp header.  We need
 93  * to find the appropriate port.
 94  */
 95 void
 96 udp_err(int err, unsigned char *header, unsigned long daddr,
 97         unsigned long saddr, struct inet_protocol *protocol)
 98 {
 99   struct udphdr *th;
100   struct sock *sk;
101   struct iphdr *ip=(struct iphdr *)header;
102   
103   header += 4*ip->ihl;
104   
105   th = (struct udphdr *)header;  
106    
107   DPRINTF((DBG_UDP,"UDP: err(err=%d, header=%X, daddr=%X, saddr=%X, protocl=%X)\n\
108 sport=%d,dport=%d", err, header, daddr, saddr, protocol, (int)th->source,(int)th->dest));
109 
110   sk = get_sock(&udp_prot, th->source, daddr, th->dest, saddr);
111 
112   if (sk == NULL) 
113         return; /* No socket for error */
114         
115   if (err < 0)          /* As per the calling spec */
116   {
117         sk->err = -err;
118         sk->error_report(sk);           /* User process wakes to see error */
119         return;
120   }
121   
122   if (err & 0xff00 ==(ICMP_SOURCE_QUENCH << 8)) {       /* Slow down! */
123         if (sk->cong_window > 1) 
124                 sk->cong_window = sk->cong_window/2;
125         return;
126   }
127 
128   sk->err = icmp_err_convert[err & 0xff].errno;
129 
130   /* It's only fatal if we have connected to them. */
131   if (icmp_err_convert[err & 0xff].fatal && sk->state == TCP_ESTABLISHED) {
132         sk->err=ECONNREFUSED;
133   }
134   sk->error_report(sk);
135 }
136 
137 
138 static unsigned short
139 udp_check(struct udphdr *uh, int len,
140           unsigned long saddr, unsigned long daddr)
141 {
142   unsigned long sum;
143 
144   DPRINTF((DBG_UDP, "UDP: check(uh=%X, len = %d, saddr = %X, daddr = %X)\n",
145                                                         uh, len, saddr, daddr));
146 
147   print_udp(uh);
148 
149   __asm__("\t addl %%ecx,%%ebx\n"
150           "\t adcl %%edx,%%ebx\n"
151           "\t adcl $0, %%ebx\n"
152           : "=b"(sum)
153           : ""(daddr), "c"(saddr), "d"((ntohs(len) << 16) + IPPROTO_UDP*256)
154           : "cx","bx","dx" );
155 
156   if (len > 3) {
157         __asm__("\tclc\n"
158                 "1:\n"
159                 "\t lodsl\n"
160                 "\t adcl %%eax, %%ebx\n"
161                 "\t loop 1b\n"
162                 "\t adcl $0, %%ebx\n"
163                 : "=b"(sum) , "=S"(uh)
164                 : ""(sum), "c"(len/4) ,"1"(uh)
165                 : "ax", "cx", "bx", "si" );
166   }
167 
168   /* Convert from 32 bits to 16 bits. */
169   __asm__("\t movl %%ebx, %%ecx\n"
170           "\t shrl $16,%%ecx\n"
171           "\t addw %%cx, %%bx\n"
172           "\t adcw $0, %%bx\n"
173           : "=b"(sum)
174           : ""(sum)
175           : "bx", "cx");
176 
177   /* Check for an extra word. */
178   if ((len & 2) != 0) {
179         __asm__("\t lodsw\n"
180                 "\t addw %%ax,%%bx\n"
181                 "\t adcw $0, %%bx\n"
182                 : "=b"(sum), "=S"(uh)
183                 : ""(sum) ,"1"(uh)
184                 : "si", "ax", "bx");
185   }
186 
187   /* Now check for the extra byte. */
188   if ((len & 1) != 0) {
189         __asm__("\t lodsb\n"
190                 "\t movb $0,%%ah\n"
191                 "\t addw %%ax,%%bx\n"
192                 "\t adcw $0, %%bx\n"
193                 : "=b"(sum)
194                 : ""(sum) ,"S"(uh)
195                 : "si", "ax", "bx");
196   }
197 
198   /* We only want the bottom 16 bits, but we never cleared the top 16. */
199   return((~sum) & 0xffff);
200 }
201 
202 
203 static void
204 udp_send_check(struct udphdr *uh, unsigned long saddr, 
205                unsigned long daddr, int len, struct sock *sk)
206 {
207   uh->check = 0;
208   if (sk && sk->no_check) 
209         return;
210   uh->check = udp_check(uh, len, saddr, daddr);
211   if (uh->check == 0) uh->check = 0xffff;
212 }
213 
214 
215 static int
216 udp_send(struct sock *sk, struct sockaddr_in *sin,
217          unsigned char *from, int len)
218 {
219   struct sk_buff *skb;
220   struct device *dev;
221   struct udphdr *uh;
222   unsigned char *buff;
223   unsigned long saddr;
224   int size, tmp;
225   int err;
226   
227   DPRINTF((DBG_UDP, "UDP: send(dst=%s:%d buff=%X len=%d)\n",
228                 in_ntoa(sin->sin_addr.s_addr), ntohs(sin->sin_port),
229                 from, len));
230 
231   err=verify_area(VERIFY_READ, from, len);
232   if(err)
233         return(err);
234 
235   /* Allocate a copy of the packet. */
236   size = sizeof(struct sk_buff) + sk->prot->max_header + len;
237   skb = sk->prot->wmalloc(sk, size, 0, GFP_KERNEL);
238   if (skb == NULL) return(-ENOMEM);
239 
240   skb->mem_addr = skb;
241   skb->mem_len  = size;
242   skb->sk       = NULL; /* to avoid changing sk->saddr */
243   skb->free     = 1;
244   skb->arp      = 0;
245 
246   /* Now build the IP and MAC header. */
247   buff = skb->data;
248   saddr = 0;
249   dev = NULL;
250   DPRINTF((DBG_UDP, "UDP: >> IP_Header: %X -> %X dev=%X prot=%X len=%d\n",
251                         saddr, sin->sin_addr.s_addr, dev, IPPROTO_UDP, skb->mem_len));
252   tmp = sk->prot->build_header(skb, saddr, sin->sin_addr.s_addr,
253                                &dev, IPPROTO_UDP, sk->opt, skb->mem_len,sk->ip_tos,sk->ip_ttl);
254   skb->sk=sk;   /* So memory is freed correctly */
255                             
256   if (tmp < 0 ) {
257         sk->prot->wfree(sk, skb->mem_addr, skb->mem_len);
258         return(tmp);
259   }
260   buff += tmp;
261   saddr = dev->pa_addr;
262   DPRINTF((DBG_UDP, "UDP: >> MAC+IP len=%d\n", tmp));
263 
264   skb->len = tmp + sizeof(struct udphdr) + len; /* len + UDP + IP + MAC */
265   skb->dev = dev;
266 #ifdef OLD
267   /*
268    * This code used to hack in some form of fragmentation.
269    * I removed that, since it didn't work anyway, and it made the
270    * code a bad thing to read and understand. -FvK
271    */
272   if (len > dev->mtu) {
273 #else
274   if (skb->len > 4095)
275   {
276 #endif    
277         printk("UDP: send: length %d > mtu %d (ignored)\n", len, dev->mtu);
278         sk->prot->wfree(sk, skb->mem_addr, skb->mem_len);
279         return(-EMSGSIZE);
280   }
281 
282   /* Fill in the UDP header. */
283   uh = (struct udphdr *) buff;
284   uh->len = htons(len + sizeof(struct udphdr));
285   uh->source = sk->dummy_th.source;
286   uh->dest = sin->sin_port;
287   buff = (unsigned char *) (uh + 1);
288 
289   /* Copy the user data. */
290   memcpy_fromfs(buff, from, len);
291 
292   /* Set up the UDP checksum. */
293   udp_send_check(uh, saddr, sin->sin_addr.s_addr, skb->len - tmp, sk);
294 
295   /* Send the datagram to the interface. */
296   sk->prot->queue_xmit(sk, dev, skb, 1);
297 
298   return(len);
299 }
300 
301 
302 static int
303 udp_sendto(struct sock *sk, unsigned char *from, int len, int noblock,
304            unsigned flags, struct sockaddr_in *usin, int addr_len)
305 {
306   struct sockaddr_in sin;
307   int tmp;
308   int err;
309 
310   DPRINTF((DBG_UDP, "UDP: sendto(len=%d, flags=%X)\n", len, flags));
311 
312   /* Check the flags. */
313   if (flags) 
314         return(-EINVAL);
315   if (len < 0) 
316         return(-EINVAL);
317   if (len == 0) 
318         return(0);
319 
320   /* Get and verify the address. */
321   if (usin) {
322         if (addr_len < sizeof(sin)) return(-EINVAL);
323         err=verify_area(VERIFY_READ, usin, sizeof(sin));
324         if(err)