1 /* $NetBSD: vstream_tweak.c,v 1.2 2017/02/14 01:16:49 christos Exp $ */ 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 #include <errno.h> 46 47 /* Utility library. */ 48 49 #include <msg.h> 50 #include <vstream.h> 51 52 /* Application-specific. */ 53 54 #ifdef HAS_IPV6 55 #define SOCKADDR_STORAGE struct sockaddr_storage 56 #else 57 #define SOCKADDR_STORAGE struct sockaddr 58 #endif 59 60 /* vstream_tweak_sock - boost your generic network performance */ 61 62 int vstream_tweak_sock(VSTREAM *fp) 63 { 64 SOCKADDR_STORAGE ss; 65 struct sockaddr *sa = (struct sockaddr *) &ss; 66 SOCKADDR_SIZE sa_length = sizeof(ss); 67 int ret; 68 69 /* 70 * If the caller doesn't know if this socket is AF_LOCAL, AF_INET, etc., 71 * figure it out for them. 72 */ 73 if ((ret = getsockname(vstream_fileno(fp), sa, &sa_length)) >= 0) { 74 switch (sa->sa_family) { 75 #ifdef AF_INET6 76 case AF_INET6: 77 #endif 78 case AF_INET: 79 ret = vstream_tweak_tcp(fp); 80 break; 81 } 82 } 83 return (ret); 84 } 85 86 /* vstream_tweak_tcp - boost your TCP performance */ 87 88 int vstream_tweak_tcp(VSTREAM *fp) 89 { 90 const char *myname = "vstream_tweak_tcp"; 91 int mss = 0; 92 SOCKOPT_SIZE mss_len = sizeof(mss); 93 int err; 94 95 /* 96 * Avoid Nagle delays when VSTREAM buffers are smaller than the MSS. 97 * 98 * Forcing TCP_NODELAY to be "always on" would hurt performance in the 99 * common case where VSTREAM buffers are larger than the MSS. 100 * 101 * Instead we ask the kernel what the current MSS is, and take appropriate 102 * action. Linux <= 2.2 getsockopt(TCP_MAXSEG) always returns zero (or 103 * whatever value was stored last with setsockopt()). 104 * 105 * Some ancient FreeBSD kernels don't report 'host unreachable' errors with 106 * getsockopt(SO_ERROR), and then treat getsockopt(TCP_MAXSEG) as a NOOP, 107 * leaving the mss parameter value unchanged. To work around these two 108 * getsockopt() bugs we set mss = 0, which is a harmless value. 109 */ 110 if ((err = getsockopt(vstream_fileno(fp), IPPROTO_TCP, TCP_MAXSEG, 111 (void *) &mss, &mss_len)) < 0 112 && errno != ECONNRESET) { 113 msg_warn("%s: getsockopt TCP_MAXSEG: %m", myname); 114 return (err); 115 } 116 if (msg_verbose) 117 msg_info("%s: TCP_MAXSEG %d", myname, mss); 118 119 /* 120 * Fix for recent Postfix versions: increase the VSTREAM buffer size if 121 * it is smaller than the MSS. Note: the MSS may change when the route 122 * changes and IP path MTU discovery is turned on, so we choose a 123 * somewhat larger buffer. 124 * 125 * Note: as of 20120527, the CA_VSTREAM_CTL_BUFSIZE request can reduce the 126 * stream buffer size to less than VSTREAM_BUFSIZE, when the request is 127 * made before the first stream read or write operation. We don't want to 128 * reduce the buffer size. 129 */ 130 #define EFF_BUFFER_SIZE(fp) (vstream_req_bufsize(fp) ? \ 131 vstream_req_bufsize(fp) : VSTREAM_BUFSIZE) 132 133 #ifdef CA_VSTREAM_CTL_BUFSIZE 134 if (mss > EFF_BUFFER_SIZE(fp) / 2) { 135 if (mss < INT_MAX / 2) 136 mss *= 2; 137 vstream_control(fp, 138 CA_VSTREAM_CTL_BUFSIZE(mss), 139 CA_VSTREAM_CTL_END); 140 } 141 142 /* 143 * Workaround for older Postfix versions: turn on TCP_NODELAY if the 144 * VSTREAM buffer size is smaller than the MSS. 145 */ 146 #else 147 if (mss > VSTREAM_BUFSIZE) { 148 int nodelay = 1; 149 150 if ((err = setsockopt(vstream_fileno(fp), IPPROTO_TCP, TCP_NODELAY, 151 (void *) &nodelay, sizeof(nodelay))) < 0 152 && errno != ECONNRESET) 153 msg_warn("%s: setsockopt TCP_NODELAY: %m", myname); 154 } 155 #endif 156 return (err); 157 } 158