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

   1 /*      $NetBSD$        */
   2
   3 /*++
   4 /* NAME
   5 /*      vstream_tweak 3
   6 /* SUMMARY
   7 /*      performance tweaks
   8 /* SYNOPSIS
   9 /*      #include <vstream.h>
  10 /*
  11 /*      VSTREAM *vstream_tweak_sock(stream)
  12 /*      VSTREAM *stream;
  13 /*
  14 /*      VSTREAM *vstream_tweak_tcp(stream)
  15 /*      VSTREAM *stream;
  16 /* DESCRIPTION
  17 /*      vstream_tweak_sock() does a best effort to boost your
  18 /*      network performance on the specified generic stream.
  19 /*
  20 /*      vstream_tweak_tcp() does a best effort to boost your
  21 /*      Internet performance on the specified TCP stream.
  22 /*
  23 /*      Arguments:
  24 /* .IP stream
  25 /*      The stream being boosted.
  26 /* DIAGNOSTICS
  27 /*      Panics: interface violations.
  28 /* LICENSE
  29 /* .ad
  30 /* .fi
  31 /*      The Secure Mailer license must be distributed with this software.
  32 /* AUTHOR(S)
  33 /*      Wietse Venema
  34 /*      IBM T.J. Watson Research
  35 /*      P.O. Box 704
  36 /*      Yorktown Heights, NY 10598, USA
  37 /*--*/
  38
  39 /* System library. */
  40
  41 #include <sys_defs.h>
  42 #include <sys/socket.h>
  43 #include <netinet/in.h>
  44 #include <netinet/tcp.h>
  45
  46 /* Utility library. */
  47
  48 #include <msg.h>
  49 #include <vstream.h>
  50
  51 /* Application-specific. */
  52
  53 #ifdef HAS_IPV6
  54 #define SOCKADDR_STORAGE struct sockaddr_storage
  55 #else
  56 #define SOCKADDR_STORAGE struct sockaddr
  57 #endif
  58
  59 /* vstream_tweak_sock - boost your generic network performance */
  60
  61 int     vstream_tweak_sock(VSTREAM *fp)
  62 {
  63     SOCKADDR_STORAGE ss;
  64     struct sockaddr *sa = (struct sockaddr *) & ss;
  65     SOCKADDR_SIZE sa_length = sizeof(ss);
  66     int     ret;
  67
  68     /*
  69      * If the caller doesn't know if this socket is AF_LOCAL, AF_INET, etc.,
  70      * figure it out for them.
  71      */
  72     if ((ret = getsockname(vstream_fileno(fp), sa, &sa_length)) >= 0) {
  73         switch (sa->sa_family) {
  74 #ifdef AF_INET6
  75         case AF_INET6:
  76 #endif
  77         case AF_INET:
  78             ret = vstream_tweak_tcp(fp);
  79             break;
  80         }
  81     }
  82     return (ret);
  83 }
  84
  85 /* vstream_tweak_tcp - boost your TCP performance */
  86
  87 int     vstream_tweak_tcp(VSTREAM *fp)
  88 {
  89     const char *myname = "vstream_tweak_tcp";
  90     int     mss;
  91     SOCKOPT_SIZE mss_len = sizeof(mss);
  92     int     err;
  93
  94     /*
  95      * Avoid Nagle delays when VSTREAM buffers are smaller than the MSS.
  96      *
  97      * Forcing TCP_NODELAY to be "always on" would hurt performance in the
  98      * common case where VSTREAM buffers are larger than the MSS.
  99      *
 100      * Instead we ask the kernel what the current MSS is, and take appropriate
 101      * action. Linux <= 2.2 getsockopt(TCP_MAXSEG) always returns zero (or
 102      * whatever value was stored last with setsockopt()).
 103      */
 104     if ((err = getsockopt(vstream_fileno(fp), IPPROTO_TCP, TCP_MAXSEG,
 105                           (char *) &mss, &mss_len)) < 0) {
 106         msg_warn("%s: getsockopt TCP_MAXSEG: %m", myname);
 107         return (err);
 108     }
 109     if (msg_verbose)
 110         msg_info("%s: TCP_MAXSEG %d", myname, mss);
 111
 112     /*
 113      * Fix for recent Postfix versions: increase the VSTREAM buffer size if
 114      * the VSTREAM buffer is smaller than the MSS. Note: the MSS may change
 115      * when the route changes and IP path MTU discovery is turned on, so we
 116      * choose a somewhat larger buffer.
 117      */
 118 #ifdef VSTREAM_CTL_BUFSIZE
 119     if (mss > 0) {
 120         if (mss < INT_MAX / 2)
 121             mss *= 2;
 122         vstream_control(fp,
 123                         VSTREAM_CTL_BUFSIZE, (ssize_t) mss,
 124                         VSTREAM_CTL_END);
 125     }
 126
 127     /*
 128      * Workaround for older Postfix versions: turn on TCP_NODELAY if the
 129      * VSTREAM buffer size is smaller than the MSS.
 130      */
 131 #else
 132     if (mss > VSTREAM_BUFSIZE) {
 133         int     nodelay = 1;
 134
 135         if ((err = setsockopt(vstream_fileno(fp), IPPROTO_TCP, TCP_NODELAY,
 136                               (char *) &nodelay, sizeof(nodelay))) < 0)
 137             msg_warn("%s: setsockopt TCP_NODELAY: %m", myname);
 138     }
 139 #endif
 140     return (err);
 141 }