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List:       ipfilter
Subject:    Re: Patch for ftp proxy on BSDI
From:       Scott Presnell <srp () zgi ! com>
Date:       1999-09-27 14:38:10
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Darren Reed wrote:
> 
> Please do not laugh at how trivial this change is.  For some reason,
> without that cast, the htons() on the u_char (ip->ip_p) was setting
> the upper 8 bits to non-zero and corrupting the checksum result.
> 
> Darren

It might be worthwhile checking all of the IP Filter code for this
(non) promotion.  I ran into a similar u_char => u_short issue in the
rcmd proxy (was fixed in 3.2.2) under NetBSD 1.4.1 (another BSD 4.4
derived unix).

	Thanks.

	- Scott

> Index: fil.c
> ===================================================================
> RCS file: /devel/CVS/IP-Filter/fil.c,v
> retrieving revision 2.3.2.3
> diff -c -r2.3.2.3 fil.c
> *** fil.c       1999/09/21 11:56:19     2.3.2.3
> --- fil.c       1999/09/27 14:10:04
> ***************
> *** 990,996 ****
>          */
>         hlen = ip->ip_hl << 2;
>         slen = ip->ip_len - hlen;
> !       sum = htons(ip->ip_p);
>         sum += htons(slen);
>         sp = (u_short *)&ip->ip_src;
>         sum += *sp++;   /* ip_src */
> --- 990,996 ----
>          */
>         hlen = ip->ip_hl << 2;
>         slen = ip->ip_len - hlen;
> !       sum = htons((u_short)ip->ip_p);
>         sum += htons(slen);
>         sp = (u_short *)&ip->ip_src;
>         sum += *sp++;   /* ip_src */

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