net: ipv4: fix multipath RTM_GETROUTE behavior when iif is given (bbadb9a2) · Commits · 戴 / test

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:

Florian Larysch <fl@n621.de> Signed-off-by:

David S. Miller <davem@davemloft.net>

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;

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