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      1 /*	$NetBSD: inet_windowsize.c,v 1.2 2017/02/14 01:16:49 christos Exp $	*/
      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, (void *) &windowsize,
     79 		   sizeof(windowsize)) < 0)
     80 	msg_warn("setsockopt SO_SNDBUF %d: %m", windowsize);
     81     if (setsockopt(sock, SOL_SOCKET, SO_RCVBUF, (void *) &windowsize,
     82 		   sizeof(windowsize)) < 0)
     83 	msg_warn("setsockopt SO_RCVBUF %d: %m", windowsize);
     84 }
     85