Commit d6d5e999 authored Apr 08, 2016 by Chris Friesen Committed by David S. Miller Apr 13, 2016

route: do not cache fib route info on local routes with oif



For local routes that require a particular output interface we do not want
to cache the result.  Caching the result causes incorrect behaviour when
there are multiple source addresses on the interface.  The end result
being that if the intended recipient is waiting on that interface for the
packet he won't receive it because it will be delivered on the loopback
interface and the IP_PKTINFO ipi_ifindex will be set to the loopback
interface as well.

This can be tested by running a program such as "dhcp_release" which
attempts to inject a packet on a particular interface so that it is
received by another program on the same board.  The receiving process
should see an IP_PKTINFO ipi_ifndex value of the source interface
(e.g., eth1) instead of the loopback interface (e.g., lo).  The packet
will still appear on the loopback interface in tcpdump but the important
aspect is that the CMSG info is correct.

Sample dhcp_release command line:

   dhcp_release eth1 192.168.204.222 02:11:33:22:44:66

Signed-off-by: Allain Legacy <allain.legacy@windriver.com>
Signed off-by: Chris Friesen <chris.friesen@windriver.com>
Reviewed-by: Julian Anastasov <ja@ssi.bg>
Signed-off-by: David S. Miller <davem@davemloft.net>

parent 65c66af6

net/ipv4/route.c

+12 −0

Original line number	Diff line number	Diff line
		@@ -2046,6 +2046,18 @@ static struct rtable __mkroute_output(const struct fib_result res,
		*/
		if (fi && res->prefixlen < 4)
		fi = NULL;
		} else if ((type == RTN_LOCAL) && (orig_oif != 0) &&
		(orig_oif != dev_out->ifindex)) {
		/* For local routes that require a particular output interface
		* we do not want to cache the result. Caching the result
		* causes incorrect behaviour when there are multiple source
		* addresses on the interface, the end result being that if the
		* intended recipient is waiting on that interface for the
		* packet he won't receive it because it will be delivered on
		* the loopback interface and the IP_PKTINFO ipi_ifindex will
		* be set to the loopback interface as well.
		*/
		fi = NULL;
		}

		fnhe = NULL;

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