inet_windowsize.c

[詳解]

/*++
/* NAME
/*  inet_windowsize 3
/* SUMMARY
/*  TCP window scaling control
/* SYNOPSIS
/*  #include <iostuff.h>
/*
/*  int inet_windowsize;
/*
/*  void    set_inet_windowsize(sock, windowsize)
/*  int sock;
/*  int windowsize;
/* DESCRIPTION
/*  set_inet_windowsize() overrides the default TCP window size
/*  with the specified value. When called before listen() or
/*  accept(), this works around broken infrastructure that
/*  mis-handles TCP window scaling options.
/*
/*  The global inet_windowsize variable is available for other
/*  routines to remember that they wish to override the default
/*  TCP window size. The variable is not accessed by the
/*  set_inet_windowsize() function itself.
/*
/*  Arguments:
/* .IP sock
/*  TCP communication endpoint, before the connect(2) or listen(2) call.
/* .IP windowsize
/*  The preferred TCP window size. This must be > 0.
/* DIAGNOSTICS
/*  Panic: interface violation.
/*  Warnings: some error return from setsockopt().
/* 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 libraries. */

#include <sys_defs.h>
#include <sys/socket.h>

/* Utility library. */

#include <msg.h>
#include <iostuff.h>

/* Application storage. */

 /*
  * Tunable to work around broken routers.
  */
int     inet_windowsize = 0;

/* set_inet_windowsize - set TCP send/receive window size */

void    set_inet_windowsize(int sock, int windowsize)
{

    /*
     * Sanity check.
     */
    if (windowsize <= 0)
    msg_panic("inet_windowsize: bad window size %d", windowsize);

    /*
     * Generic implementation: set the send and receive buffer size before
     * listen() or connect().
     */
    if (setsockopt(sock, SOL_SOCKET, SO_SNDBUF, (void *) &windowsize,
           sizeof(windowsize)) < 0)
    msg_warn("setsockopt SO_SNDBUF %d: %m", windowsize);
    if (setsockopt(sock, SOL_SOCKET, SO_RCVBUF, (void *) &windowsize,
           sizeof(windowsize)) < 0)
    msg_warn("setsockopt SO_RCVBUF %d: %m", windowsize);
}