external/ibm-public/postfix/dist/src/util/inet_windowsize.c

   1 /*      $NetBSD$        */
   2
   3 /*++
   4 /* NAME
   5 /*      inet_windowsize 3
   6 /* SUMMARY
   7 /*      TCP window scaling control
   8 /* SYNOPSIS
   9 /*      #include <iostuff.h>
  10 /*
  11 /*      int     inet_windowsize;
  12 /*
  13 /*      void    set_inet_windowsize(sock, windowsize)
  14 /*      int     sock;
  15 /*      int     windowsize;
  16 /* DESCRIPTION
  17 /*      set_inet_windowsize() overrides the default TCP window size
  18 /*      with the specified value. When called before listen() or
  19 /*      accept(), this works around broken infrastructure that
  20 /*      mis-handles TCP window scaling options.
  21 /*
  22 /*      The global inet_windowsize variable is available for other
  23 /*      routines to remember that they wish to override the default
  24 /*      TCP window size. The variable is not accessed by the
  25 /*      set_inet_windowsize() function itself.
  26 /*
  27 /*      Arguments:
  28 /* .IP sock
  29 /*      TCP communication endpoint, before the connect(2) or listen(2) call.
  30 /* .IP windowsize
  31 /*      The preferred TCP window size. This must be > 0.
  32 /* DIAGNOSTICS
  33 /*      Panic: interface violation.
  34 /*      Warnings: some error return from setsockopt().
  35 /* LICENSE
  36 /* .ad
  37 /* .fi
  38 /*      The Secure Mailer license must be distributed with this software.
  39 /* AUTHOR(S)
  40 /*      Wietse Venema
  41 /*      IBM T.J. Watson Research
  42 /*      P.O. Box 704
  43 /*      Yorktown Heights, NY 10598, USA
  44 /*--*/
  45
  46 /* System libraries. */
  47
  48 #include <sys_defs.h>
  49 #include <sys/socket.h>
  50
  51 /* Utility library. */
  52
  53 #include <msg.h>
  54 #include <iostuff.h>
  55
  56 /* Application storage. */
  57
  58  /*
  59   * Tunable to work around broken routers.
  60   */
  61 int     inet_windowsize = 0;
  62
  63 /* set_inet_windowsize - set TCP send/receive window size */
  64
  65 void    set_inet_windowsize(int sock, int windowsize)
  66 {
  67
  68     /*
  69      * Sanity check.
  70      */
  71     if (windowsize <= 0)
  72         msg_panic("inet_windowsize: bad window size %d", windowsize);
  73
  74     /*
  75      * Generic implementation: set the send and receive buffer size before
  76      * listen() or connect().
  77      */
  78     if (setsockopt(sock, SOL_SOCKET, SO_SNDBUF, (char *) &windowsize,
  79                    sizeof(windowsize)) < 0)
  80         msg_warn("setsockopt SO_SNDBUF %d: %m", windowsize);
  81     if (setsockopt(sock, SOL_SOCKET, SO_RCVBUF, (char *) &windowsize,
  82                    sizeof(windowsize)) < 0)
  83         msg_warn("setsockopt SO_RCVBUF %d: %m", windowsize);
  84 }