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 *inet_protos[MAX_INET_PROTOS] ____cacheline_aligned_in_smp;
  32static DEFINE_SPINLOCK(inet_proto_lock);
  33
  34/*
  35 *      Add a protocol handler to the hash tables
  36 */
  37
  38int inet_add_protocol(const struct net_protocol *prot, unsigned char protocol)
  39{
  40        int hash, ret;
  41
  42        hash = protocol & (MAX_INET_PROTOS - 1);
  43
  44        spin_lock_bh(&inet_proto_lock);
  45        if (inet_protos[hash]) {
  46                ret = -1;
  47        } else {
  48                inet_protos[hash] = prot;
  49                ret = 0;
  50        }
  51        spin_unlock_bh(&inet_proto_lock);
  52
  53        return ret;
  54}
  55
  56/*
  57 *      Remove a protocol from the hash tables.
  58 */
  59
  60int inet_del_protocol(const struct net_protocol *prot, unsigned char protocol)
  61{
  62        int hash, ret;
  63
  64        hash = protocol & (MAX_INET_PROTOS - 1);
  65
  66        spin_lock_bh(&inet_proto_lock);
  67        if (inet_protos[hash] == prot) {
  68                inet_protos[hash] = NULL;
  69                ret = 0;
  70        } else {
  71                ret = -1;
  72        }
  73        spin_unlock_bh(&inet_proto_lock);
  74
  75        synchronize_net();
  76
  77        return ret;
  78}
  79
  80EXPORT_SYMBOL(inet_add_protocol);
  81EXPORT_SYMBOL(inet_del_protocol);
  82