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 *inet_protos[MAX_INET_PROTOS] ____cacheline_aligned_in_smp;
  32 static DEFINE_SPINLOCK(inet_proto_lock);
  33
  34 /*
  35  *      Add a protocol handler to the hash tables
  36  */
  37
  38 int 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
  60 int 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
  80 EXPORT_SYMBOL(inet_add_protocol);
  81 EXPORT_SYMBOL(inet_del_protocol);