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Pick the smallest possible TCP window scaling factor that will still allow

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us to scale up to sb_max.  This might fix the problems with some firewalls.

Taken from FreeBSD (silby).
OK by <dyoung>.
This commit is contained in:
rmind 2007-11-04 11:04:26 +00:00
parent 89eb056b33
commit d63e75f696
2 changed files with 23 additions and 14 deletions
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26
sys/netinet/tcp_input.c
View File

@ -1,4 +1,4 @@
/* $NetBSD: tcp_input.c,v 1.270 2007/08/02 13:06:30 yamt Exp $ */
/* $NetBSD: tcp_input.c,v 1.271 2007/11/04 11:04:26 rmind Exp $ */
/*
* Copyright (C) 1995, 1996, 1997, and 1998 WIDE Project.
@ -152,7 +152,7 @@
*/
#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: tcp_input.c,v 1.270 2007/08/02 13:06:30 yamt Exp $");
__KERNEL_RCSID(0, "$NetBSD: tcp_input.c,v 1.271 2007/11/04 11:04:26 rmind Exp $");
#include "opt_inet.h"
#include "opt_ipsec.h"
@ -4086,17 +4086,27 @@ syn_cache_add(struct sockaddr *src, struct sockaddr *dst, struct tcphdr *th,
sc->sc_requested_s_scale = tb.requested_s_scale;
sc->sc_request_r_scale = 0;
/*
* Compute proper scaling value from buffer space.
* Leave enough room for the socket buffer to grow
* with auto sizing. This allows us to scale the
* receive buffer over a wide range while not losing
* any efficiency or fine granularity.
* Pick the smallest possible scaling factor that
* will still allow us to scale up to sb_max.
*
* We do this because there are broken firewalls that
* will corrupt the window scale option, leading to
* the other endpoint believing that our advertised
* window is unscaled. At scale factors larger than
* 5 the unscaled window will drop below 1500 bytes,
* leading to serious problems when traversing these
* broken firewalls.
*
* With the default sbmax of 256K, a scale factor
* of 3 will be chosen by this algorithm. Those who
* choose a larger sbmax should watch out
* for the compatiblity problems mentioned above.
*
* RFC1323: The Window field in a SYN (i.e., a <SYN>
* or <SYN,ACK>) segment itself is never scaled.
*/
while (sc->sc_request_r_scale < TCP_MAX_WINSHIFT &&
(0x1 << sc->sc_request_r_scale) < tcp_minmss)
(TCP_MAXWIN << sc->sc_request_r_scale) < sb_max)
sc->sc_request_r_scale++;
} else {
sc->sc_requested_s_scale = 15;

11
sys/netinet/tcp_usrreq.c
View File

@ -1,4 +1,4 @@
/* $NetBSD: tcp_usrreq.c,v 1.137 2007/09/19 04:33:44 dyoung Exp $ */
/* $NetBSD: tcp_usrreq.c,v 1.138 2007/11/04 11:04:27 rmind Exp $ */
/*
* Copyright (C) 1995, 1996, 1997, and 1998 WIDE Project.
@ -102,7 +102,7 @@
*/
#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: tcp_usrreq.c,v 1.137 2007/09/19 04:33:44 dyoung Exp $");
__KERNEL_RCSID(0, "$NetBSD: tcp_usrreq.c,v 1.138 2007/11/04 11:04:27 rmind Exp $");
#include "opt_inet.h"
#include "opt_ipsec.h"
@ -431,12 +431,11 @@ tcp_usrreq(struct socket *so, int req,
break;
}
/*
* Compute window scaling to request:
* XXX: This should be moved to tcp_output(),
* and should be based on the actual MSS.
* Compute window scaling to request.
* XXX: This should be moved to tcp_output().
*/
while (tp->request_r_scale < TCP_MAX_WINSHIFT &&
(0x1 << tp->request_r_scale) < tcp_minmss)
(TCP_MAXWIN << tp->request_r_scale) < sb_max)
tp->request_r_scale++;
soisconnecting(so);
tcpstat.tcps_connattempt++;