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tcp, udp: Don't pre-fill IPv4 destination address in headers

Because packets sent on the tap interface will always be going to the
guest/namespace, we more-or-less know what address they'll be going to.  So
we pre-fill this destination address in our header buffers for IPv4.  We
can't do the same for IPv6 because we could need either the global or
link-local address for the guest.  In future we're going to want more
flexibility for the destination address, so this pre-filling will get in
the way.

Change the flow so we always fill in the IPv4 destination address for each
packet, rather than prefilling it from proto_update_l2_buf().  In fact for
TCP we already redundantly filled the destination for each packet anyway.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
This commit is contained in:
David Gibson 2023-08-22 15:29:57 +10:00 committed by Stefano Brivio
parent 5bf200ae8a
commit 955dd3251c
8 changed files with 15 additions and 32 deletions

10
passt.c
View file

@ -117,13 +117,11 @@ static void timer_init(struct ctx *c, const struct timespec *now)
* proto_update_l2_buf() - Update scatter-gather L2 buffers in protocol handlers
* @eth_d: Ethernet destination address, NULL if unchanged
* @eth_s: Ethernet source address, NULL if unchanged
* @ip_da: Pointer to IPv4 destination address, NULL if unchanged
*/
void proto_update_l2_buf(const unsigned char *eth_d, const unsigned char *eth_s,
const struct in_addr *ip_da)
void proto_update_l2_buf(const unsigned char *eth_d, const unsigned char *eth_s)
{
tcp_update_l2_buf(eth_d, eth_s, ip_da);
udp_update_l2_buf(eth_d, eth_s, ip_da);
tcp_update_l2_buf(eth_d, eth_s);
udp_update_l2_buf(eth_d, eth_s);
}
/**
@ -247,7 +245,7 @@ int main(int argc, char **argv)
if (!c.no_icmp)
icmp_init();
proto_update_l2_buf(c.mac_guest, c.mac, &c.ip4.addr);
proto_update_l2_buf(c.mac_guest, c.mac);
if (c.ifi4 && !c.no_dhcp)
dhcp_init();