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Commit bbadb9a2 authored by Florian Larysch's avatar Florian Larysch Committed by David S. Miller
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net: ipv4: fix multipath RTM_GETROUTE behavior when iif is given 



inet_rtm_getroute synthesizes a skeletal ICMP skb, which is passed to
ip_route_input when iif is given. If a multipath route is present for
the designated destination, fib_multipath_hash ends up being called with
that skb. However, as that skb contains no information beyond the
protocol type, the calculated hash does not match the one we would see
for a real packet.

There is currently no way to fix this for layer 4 hashing, as
RTM_GETROUTE doesn't have the necessary information to create layer 4
headers. To fix this for layer 3 hashing, set appropriate saddr/daddrs
in the skb and also change the protocol to UDP to avoid special
treatment for ICMP.

Signed-off-by: default avatarFlorian Larysch <fl@n621.de>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 6f551bd5

net/ipv4/route.c

+9 −4
Original line number Diff line number Diff line
@@ -2667,10 +2667,6 @@ static int inet_rtm_getroute(struct sk_buff *in_skb, struct nlmsghdr *nlh) 
	skb_reset_mac_header(skb);

	skb_reset_network_header(skb);



	/* Bugfix: need to give ip_route_input enough of an IP header to not gag. */

	ip_hdr(skb)->protocol = IPPROTO_ICMP;

	skb_reserve(skb, MAX_HEADER + sizeof(struct iphdr));



	src = tb[RTA_SRC] ? nla_get_in_addr(tb[RTA_SRC]) : 0;

	dst = tb[RTA_DST] ? nla_get_in_addr(tb[RTA_DST]) : 0;

	iif = tb[RTA_IIF] ? nla_get_u32(tb[RTA_IIF]) : 0;
@@ -2680,6 +2676,15 @@ static int inet_rtm_getroute(struct sk_buff *in_skb, struct nlmsghdr *nlh) 
	else

		uid = (iif ? INVALID_UID : current_uid());



	/* Bugfix: need to give ip_route_input enough of an IP header to

	 * not gag.

	 */

	ip_hdr(skb)->protocol = IPPROTO_UDP;

	ip_hdr(skb)->saddr = src;

	ip_hdr(skb)->daddr = dst;



	skb_reserve(skb, MAX_HEADER + sizeof(struct iphdr));



	memset(&fl4, 0, sizeof(fl4));

	fl4.daddr = dst;

	fl4.saddr = src;