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Compute IP checksums in addition to TCP checksums when necessary in the

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new 'aliased' packets.  Note, if the original packet has a bogus cksum,
we will *NOT* re-compute the cksum, therefore the new packet will also
be wrong (but passed on).

Found by:	MartinRenters@awfulhak.demon.co.uk
Reviewed by:	Brian Somers <brian@awfulhak.demon.co.uk>
Submitted by:	Charles Mott <cmott@srv.net>
This commit is contained in:
nate 1996-12-21 18:34:52 +00:00
parent 743fb64ce9
commit 8ce659b1a4
1 changed files with 17 additions and 12 deletions
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29
usr.sbin/ppp/alias.c
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@ -754,10 +754,13 @@ void
PacketAliasIn(pip)
struct ip *pip;
{
struct in_addr save_address;
int checksum_ok;
/* Save initial destination address */
save_address = pip->ip_dst;
/* Verify initial checksum */
if (IpChecksum(pip) == 0)
checksum_ok = 1;
else
checksum_ok = 0;
if ( (ntohs(pip->ip_off) & IP_OFFMASK) == 0 )
{
@ -787,8 +790,8 @@ struct ip *pip;
FragmentIn(pip);
}
/* If destination address has changed, adjust IP checksum */
if (pip->ip_dst.s_addr != save_address.s_addr)
/* adjust IP checksum, if original is correct */
if (checksum_ok == 1)
{
pip->ip_sum = 0;
pip->ip_sum = IpChecksum(pip);
@ -799,9 +802,13 @@ void
PacketAliasOut(pip)
struct ip *pip;
{
struct in_addr save_address;
int checksum_ok;
if (IpChecksum(pip) == 0)
checksum_ok = 1;
else
checksum_ok = 0;
save_address = pip->ip_src;
if ((ntohs(pip->ip_off) & IP_OFFMASK) == 0)
{
switch (pip->ip_p)
@ -819,14 +826,12 @@ struct ip *pip;
}
else
{
if (pip->ip_src.s_addr != GetAliasAddress().s_addr)
FragmentOut(pip);
FragmentOut(pip);
}
/* Adjust IP checksum if source address has been aliased */
if (pip->ip_src.s_addr != save_address.s_addr)
/* Adjust IP checksum, if original is correct */
if (checksum_ok == 1)
{
pip->ip_sum = 0;
pip->ip_sum = IpChecksum(pip);
}