[PATCH] ipv4: add description about martian source

[cgel . zte]

From: Zhang Yunkai <zhang.yunkai@xxxxxxxxxx>

When multiple containers are running in the environment and multiple
macvlan network port are configured in each container, a lot of martian
source prints will appear after martian_log is enabled.

Such as:
IPv4: martian source 173.254.95.16 from 173.254.100.109,
on dev eth0
ll header: 00000000: ff ff ff ff ff ff 40 00 ad fe 64 6d
08 06        ......@...dm..
IPv4: martian source 173.254.95.16 from 173.254.100.109,
on dev eth1
ll header: 00000000: ff ff ff ff ff ff 40 00 ad fe 64 6d
08 06        ......@...dm..

There is no description of this kind of source in the RFC1812.

Signed-off-by: Zhang Yunkai <zhang.yunkai@xxxxxxxxxx>
---
 net/ipv4/fib_frontend.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/net/ipv4/fib_frontend.c b/net/ipv4/fib_frontend.c
index 4d61ddd8a0ec..3564308e849a 100644
--- a/net/ipv4/fib_frontend.c
+++ b/net/ipv4/fib_frontend.c
@@ -436,6 +436,9 @@ int fib_validate_source(struct sk_buff *skb, __be32 src, __be32 dst,
 		if (net->ipv4.fib_has_custom_local_routes ||
 		    fib4_has_custom_rules(net))
 			goto full_check;
+		/* Within the same container,it is regarded as a martian source,
+		 * and the same host but different containers are not.
+		 */
 		if (inet_lookup_ifaddr_rcu(net, src))
 			return -EINVAL;
 
-- 
2.25.1