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/*++
/* NAME
/* vstream_tweak 3
/* SUMMARY
/* performance tweaks
/* SYNOPSIS
/* #include <vstream.h>
/*
/* VSTREAM *vstream_tweak_sock(stream)
/* VSTREAM *stream;
/*
/* VSTREAM *vstream_tweak_tcp(stream)
/* VSTREAM *stream;
/* DESCRIPTION
/* vstream_tweak_sock() does a best effort to boost your
/* network performance on the specified generic stream.
/*
/* vstream_tweak_tcp() does a best effort to boost your
/* Internet performance on the specified TCP stream.
/*
/* Arguments:
/* .IP stream
/* The stream being boosted.
/* DIAGNOSTICS
/* Panics: interface violations.
/* LICENSE
/* .ad
/* .fi
/* The Secure Mailer license must be distributed with this software.
/* AUTHOR(S)
/* Wietse Venema
/* IBM T.J. Watson Research
/* P.O. Box 704
/* Yorktown Heights, NY 10598, USA
/*--*/
/* System library. */
#include <sys_defs.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <netinet/tcp.h>
#include <errno.h>
/* Utility library. */
#include <msg.h>
#include <vstream.h>
/* Application-specific. */
#ifdef HAS_IPV6
#define SOCKADDR_STORAGE struct sockaddr_storage
#else
#define SOCKADDR_STORAGE struct sockaddr
#endif
/* vstream_tweak_sock - boost your generic network performance */
int vstream_tweak_sock(VSTREAM *fp)
{
SOCKADDR_STORAGE ss;
struct sockaddr *sa = (struct sockaddr *) &ss;
SOCKADDR_SIZE sa_length = sizeof(ss);
int ret;
/*
* If the caller doesn't know if this socket is AF_LOCAL, AF_INET, etc.,
* figure it out for them.
*/
if ((ret = getsockname(vstream_fileno(fp), sa, &sa_length)) >= 0) {
switch (sa->sa_family) {
#ifdef AF_INET6
case AF_INET6:
#endif
case AF_INET:
ret = vstream_tweak_tcp(fp);
break;
}
}
return (ret);
}
/* vstream_tweak_tcp - boost your TCP performance */
int vstream_tweak_tcp(VSTREAM *fp)
{
const char *myname = "vstream_tweak_tcp";
int mss = 0;
SOCKOPT_SIZE mss_len = sizeof(mss);
int err;
/*
* Avoid Nagle delays when VSTREAM buffers are smaller than the MSS.
*
* Forcing TCP_NODELAY to be "always on" would hurt performance in the
* common case where VSTREAM buffers are larger than the MSS.
*
* Instead we ask the kernel what the current MSS is, and take appropriate
* action. Linux <= 2.2 getsockopt(TCP_MAXSEG) always returns zero (or
* whatever value was stored last with setsockopt()).
*
* Some ancient FreeBSD kernels don't report 'host unreachable' errors with
* getsockopt(SO_ERROR), and then treat getsockopt(TCP_MAXSEG) as a NOOP,
* leaving the mss parameter value unchanged. To work around these two
* getsockopt() bugs we set mss = 0, which is a harmless value.
*/
if ((err = getsockopt(vstream_fileno(fp), IPPROTO_TCP, TCP_MAXSEG,
(void *) &mss, &mss_len)) < 0
&& errno != ECONNRESET) {
msg_warn("%s: getsockopt TCP_MAXSEG: %m", myname);
return (err);
}
if (msg_verbose)
msg_info("%s: TCP_MAXSEG %d", myname, mss);
/*
* Fix for recent Postfix versions: increase the VSTREAM buffer size if
* it is smaller than the MSS. Note: the MSS may change when the route
* changes and IP path MTU discovery is turned on, so we choose a
* somewhat larger buffer.
*
* Note: as of 20120527, the CA_VSTREAM_CTL_BUFSIZE request can reduce the
* stream buffer size to less than VSTREAM_BUFSIZE, when the request is
* made before the first stream read or write operation. We don't want to
* reduce the buffer size.
*
* As of 20190820 we increase the mss size multipler from 2x to 4x, because
* some LINUX loopback TCP stacks report an MSS of 21845 which is 3x
* smaller than the MTU of 65536. Even with a VSTREAM buffer 2x the
* reported MSS size, performance would suck due to Nagle or delayed ACK
* delays.
*/
#define EFF_BUFFER_SIZE(fp) (vstream_req_bufsize(fp) ? \
vstream_req_bufsize(fp) : VSTREAM_BUFSIZE)
#ifdef CA_VSTREAM_CTL_BUFSIZE
if (mss > EFF_BUFFER_SIZE(fp) / 4) {
if (mss < INT_MAX / 2)
mss *= 2;
if (mss < INT_MAX / 2)
mss *= 2;
vstream_control(fp,
CA_VSTREAM_CTL_BUFSIZE(mss),
CA_VSTREAM_CTL_END);
}
/*
* Workaround for older Postfix versions: turn on TCP_NODELAY if the
* VSTREAM buffer size is smaller than the MSS.
*/
#else
if (mss > VSTREAM_BUFSIZE) {
int nodelay = 1;
if ((err = setsockopt(vstream_fileno(fp), IPPROTO_TCP, TCP_NODELAY,
(void *) &nodelay, sizeof(nodelay))) < 0
&& errno != ECONNRESET)
msg_warn("%s: setsockopt TCP_NODELAY: %m", myname);
}
#endif
return (err);
}
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