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  *              INET protocol dispatch tables.
  7  *
  8  * Version:     @(#)protocol.c  1.0.5   05/25/93
  9  *
 10  * Authors:     Ross Biro, <bir7@leland.Stanford.Edu>
 11  *              Fred N. van Kempen, <waltje@uWalt.NL.Mugnet.ORG>
 12  *
 13  * Fixes:
 14  *              Alan Cox        : Ahah! udp icmp errors don't work because
 15  *                                udp_err is never called!
 16  *              Alan Cox        : Added new fields for init and ready for
 17  *                                proper fragmentation (_NO_ 4K limits!)
 18  *
 19  *              This program is free software; you can redistribute it and/or
 20  *              modify it under the terms of the GNU General Public License
 21  *              as published by the Free Software Foundation; either version
 22  *              2 of the License, or (at your option) any later version.
 23  */
 24 #include <asm/segment.h>
 25 #include <asm/system.h>
 26 #include <linux/types.h>
 27 #include <linux/kernel.h>
 28 #include <linux/sched.h>
 29 #include <linux/string.h>
 30 #include <linux/socket.h>
 31 #include <linux/in.h>
 32 #include "inet.h"
 33 #include "dev.h"
 34 #include "ip.h"
 35 #include "protocol.h"
 36 #include "tcp.h"
 37 #include "skbuff.h"
 38 #include "sock.h"
 39 #include "icmp.h"
 40 #include "udp.h"
 41 
 42 
 43 static struct inet_protocol tcp_protocol = {
 44   tcp_rcv,              /* TCP handler          */
 45   NULL,                 /* No fragment handler (and won't be for a long time) */
 46   tcp_err,              /* TCP error control    */
 47   NULL,                 /* next                 */
 48   IPPROTO_TCP,          /* protocol ID          */
 49   0,                    /* copy                 */
 50   NULL,                 /* data                 */
 51   "TCP"                 /* name                 */
 52 };
 53 
 54 
 55 static struct inet_protocol udp_protocol = {
 56   udp_rcv,              /* UDP handler          */
 57   NULL,                 /* Will be UDP fraglist handler */
 58   udp_err,              /* UDP error control    */
 59   &tcp_protocol,        /* next                 */
 60   IPPROTO_UDP,          /* protocol ID          */
 61   0,                    /* copy                 */
 62   NULL,                 /* data                 */
 63   "UDP"                 /* name                 */
 64 };
 65 
 66 
 67 static struct inet_protocol icmp_protocol = {
 68   icmp_rcv,             /* ICMP handler         */
 69   NULL,                 /* ICMP never fragments anyway */
 70   NULL,                 /* ICMP error control   */
 71   &udp_protocol,        /* next                 */
 72   IPPROTO_ICMP,         /* protocol ID          */
 73   0,                    /* copy                 */
 74   NULL,                 /* data                 */
 75   "ICMP"                /* name                 */
 76 };
 77 
 78 
 79 struct inet_protocol *inet_protocol_base = &icmp_protocol;
 80 struct inet_protocol *inet_protos[MAX_INET_PROTOS] = {
 81   NULL
 82 };
 83 
 84 
 85 struct inet_protocol *
 86 inet_get_protocol(unsigned char prot)
 87 {
 88   unsigned char hash;
 89   struct inet_protocol *p;
 90 
 91   DPRINTF((DBG_PROTO, "get_protocol (%d)\n ", prot));
 92   hash = prot & (MAX_INET_PROTOS - 1);
 93   for (p = inet_protos[hash] ; p != NULL; p=p->next) {
 94         DPRINTF((DBG_PROTO, "trying protocol %d\n", p->protocol));
 95         if (p->protocol == prot) return((struct inet_protocol *) p);
 96   }
 97   return(NULL);
 98 }
 99 
100 
101 void
102 inet_add_protocol(struct inet_protocol *prot)
103 {
104   unsigned char hash;
105   struct inet_protocol *p2;
106 
107   hash = prot->protocol & (MAX_INET_PROTOS - 1);
108   prot ->next = inet_protos[hash];
109   inet_protos[hash] = prot;
110   prot->copy = 0;
111 
112   /* Set the copy bit if we need to. */
113   p2 = (struct inet_protocol *) prot->next;
114   while(p2 != NULL) {
115         if (p2->protocol == prot->protocol) {
116                 prot->copy = 1;
117                 break;
118         }
119         p2 = (struct inet_protocol *) prot->next;
120   }
121 }
122 
123 
124 int
125 inet_del_protocol(struct inet_protocol *prot)
126 {
127   struct inet_protocol *p;
128   struct inet_protocol *lp = NULL;
129   unsigned char hash;
130 
131   hash = prot->protocol & (MAX_INET_PROTOS - 1);
132   if (prot == inet_protos[hash]) {
133         inet_protos[hash] = (struct inet_protocol *) inet_protos[hash]->next;
134         return(0);
135   }
136 
137   p = (struct inet_protocol *) inet_protos[hash];
138   while(p != NULL) {
139         /*
140          * We have to worry if the protocol being deleted is
141          * the last one on the list, then we may need to reset
142          * someones copied bit.
143          */
144         if (p->next != NULL && p->next == prot) {
145                 /*
146                  * if we are the last one with this protocol and
147                  * there is a previous one, reset its copy bit.
148                  */
149              if (p->copy == 0 && lp != NULL) lp->copy = 0;
150              p->next = prot->next;
151              return(0);
152         }
153 
154         if (p->next != NULL && p->next->protocol == prot->protocol) {
155                 lp = p;
156         }
157 
158         p = (struct inet_protocol *) p->next;
159   }
160   return(-1);
161 }
162