inet: add a redirect generation id in inetpeer

Now inetpeer is the place where we cache redirect information for ipv4
destinations, we must be able to invalidate informations when a route is
added/removed on host.

As inetpeer is not yet namespace aware, this patch adds a shared
redirect_genid, and a per inetpeer redirect_genid. This might be changed
later if inetpeer becomes ns aware.

Cache information for one inerpeer is valid as long as its
redirect_genid has the same value than global redirect_genid.

Reported-by: Arkadiusz Miśkiewicz <a.miskiewicz@gmail.com>
Tested-by: Arkadiusz Miśkiewicz <a.miskiewicz@gmail.com>
Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/net/inetpeer.h b/include/net/inetpeer.h
index 78c83e6..e9ff3fc 100644
--- a/include/net/inetpeer.h
+++ b/include/net/inetpeer.h
@@ -35,6 +35,7 @@
 
 	u32			metrics[RTAX_MAX];
 	u32			rate_tokens;	/* rate limiting for ICMP */
+	int			redirect_genid;
 	unsigned long		rate_last;
 	unsigned long		pmtu_expires;
 	u32			pmtu_orig;