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Fix a nagging divide-by-zero error resulting from the MTU discovery code

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getting triggered at a bad time.
This commit is contained in:
wollman 1995-12-20 17:42:28 +00:00
parent 44136d3b30
commit 901107a3b5
2 changed files with 40 additions and 4 deletions
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20
sys/netinet/tcp_subr.c
View File

@ -31,7 +31,7 @@
* SUCH DAMAGE.
*
* @(#)tcp_subr.c 8.2 (Berkeley) 5/24/95
* $Id: tcp_subr.c,v 1.23 1995/12/05 17:46:43 wollman Exp $
* $Id: tcp_subr.c,v 1.24 1995/12/16 02:14:19 bde Exp $
*/
#include <sys/param.h>
@ -513,7 +513,25 @@ tcp_mtudisc(inp, errno)
taop = rmx_taop(rt->rt_rmx);
offered = taop->tao_mssopt;
mss = rt->rt_rmx.rmx_mtu - sizeof(struct tcpiphdr);
if (offered)
mss = min(mss, offered);
/*
* XXX - The above conditional probably violates the TCP
* spec. The problem is that, since we don't know the
* other end's MSS, we are supposed to use a conservative
* default. But, if we do that, then MTU discovery will
* never actually take place, because the conservative
* default is much less than the MTUs typically seen
* on the Internet today. For the moment, we'll sweep
* this under the carpet.
*
* The conservative default might not actually be a problem
* if the only case this occurs is when sending an initial
* SYN with options and data to a host we've never talked
* to before. Then, they will reply with an MSS value which
* will get recorded and the new parameters should get
* recomputed. For Further Study.
*/
if (tp->t_maxopd <= mss)
return;
tp->t_maxopd = mss;

20
sys/netinet/tcp_timewait.c
View File

@ -31,7 +31,7 @@
* SUCH DAMAGE.
*
* @(#)tcp_subr.c 8.2 (Berkeley) 5/24/95
* $Id: tcp_subr.c,v 1.23 1995/12/05 17:46:43 wollman Exp $
* $Id: tcp_subr.c,v 1.24 1995/12/16 02:14:19 bde Exp $
*/
#include <sys/param.h>
@ -513,7 +513,25 @@ tcp_mtudisc(inp, errno)
taop = rmx_taop(rt->rt_rmx);
offered = taop->tao_mssopt;
mss = rt->rt_rmx.rmx_mtu - sizeof(struct tcpiphdr);
if (offered)
mss = min(mss, offered);
/*
* XXX - The above conditional probably violates the TCP
* spec. The problem is that, since we don't know the
* other end's MSS, we are supposed to use a conservative
* default. But, if we do that, then MTU discovery will
* never actually take place, because the conservative
* default is much less than the MTUs typically seen
* on the Internet today. For the moment, we'll sweep
* this under the carpet.
*
* The conservative default might not actually be a problem
* if the only case this occurs is when sending an initial
* SYN with options and data to a host we've never talked
* to before. Then, they will reply with an MSS value which
* will get recorded and the new parameters should get
* recomputed. For Further Study.
*/
if (tp->t_maxopd <= mss)
return;
tp->t_maxopd = mss;