linux/net/ipv4/protocol.c
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   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
  31const struct net_protocol __rcu *inet_protos[MAX_INET_PROTOS] __read_mostly;
  32
  33/*
  34 *      Add a protocol handler to the hash tables
  35 */
  36
  37int inet_add_protocol(const struct net_protocol *prot, unsigned char protocol)
  38{
  39        return !cmpxchg((const struct net_protocol **)&inet_protos[protocol],
  40                        NULL, prot) ? 0 : -1;
  41}
  42EXPORT_SYMBOL(inet_add_protocol);
  43
  44/*
  45 *      Remove a protocol from the hash tables.
  46 */
  47
  48int inet_del_protocol(const struct net_protocol *prot, unsigned char protocol)
  49{
  50        int ret;
  51
  52        ret = (cmpxchg((const struct net_protocol **)&inet_protos[protocol],
  53                       prot, NULL) == prot) ? 0 : -1;
  54
  55        synchronize_net();
  56
  57        return ret;
  58}
  59EXPORT_SYMBOL(inet_del_protocol);
  60
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