net/ipv4/protocol.c

   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  * Authors:     Ross Biro
   9  *              Fred N. van Kempen, <waltje@uWalt.NL.Mugnet.ORG>
  10  *
  11  * Fixes:
  12  *              Alan Cox        : Ahah! udp icmp errors don't work because
  13  *                                udp_err is never called!
  14  *              Alan Cox        : Added new fields for init and ready for
  15  *                                proper fragmentation (_NO_ 4K limits!)
  16  *              Richard Colella : Hang on hash collision
  17  *              Vince Laviano   : Modified inet_del_protocol() to correctly
  18  *                                maintain copy bit.
  19  *
  20  *              This program is free software; you can redistribute it and/or
  21  *              modify it under the terms of the GNU General Public License
  22  *              as published by the Free Software Foundation; either version
  23  *              2 of the License, or (at your option) any later version.
  24  */
  25 #include <linux/cache.h>
  26 #include <linux/module.h>
  27 #include <linux/netdevice.h>
  28 #include <linux/spinlock.h>
  29 #include <net/protocol.h>
  30
  31 const struct net_protocol __rcu *inet_protos[MAX_INET_PROTOS] __read_mostly;
  32
  33 /*
  34  *      Add a protocol handler to the hash tables
  35  */
  36
  37 int inet_add_protocol(const struct net_protocol *prot, unsigned char protocol)
  38 {
  39         int hash = protocol & (MAX_INET_PROTOS - 1);
  40
  41         return !cmpxchg((const struct net_protocol **)&inet_protos[hash],
  42                         NULL, prot) ? 0 : -1;
  43 }
  44 EXPORT_SYMBOL(inet_add_protocol);
  45
  46 /*
  47  *      Remove a protocol from the hash tables.
  48  */
  49
  50 int inet_del_protocol(const struct net_protocol *prot, unsigned char protocol)
  51 {
  52         int ret, hash = protocol & (MAX_INET_PROTOS - 1);
  53
  54         ret = (cmpxchg((const struct net_protocol **)&inet_protos[hash],
  55                        prot, NULL) == prot) ? 0 : -1;
  56
  57         synchronize_net();
  58
  59         return ret;
  60 }
  61 EXPORT_SYMBOL(inet_del_protocol);