From: liamsmith827 <redacted>
Replace an existing comment which describes obsolete fib_lookup(),
MSG_DONTROUTE and IPv6 behavior.
Signed-off-by: liamsmith827 <redacted>
---
net/ipv4/route.c | 27 +++++++++++----------------
1 file changed, 11 insertions(+), 16 deletions(-)
diff --git a/net/ipv4/route.c b/net/ipv4/route.c
index 80a2c8a3c571..ac94d8262b6e 100644
--- a/net/ipv4/route.c
+++ b/net/ipv4/route.c
@@ -2858,24 +2858,19 @@ struct rtable *ip_route_output_key_hash_rcu(struct net *net, struct flowi4 *fl4,
if (fl4->flowi4_oif &&
(ipv4_is_multicast(fl4->daddr) ||
(!fl4->flowi4_l3mdev && err == -ESRCH))) {
- /* Apparently, routing tables are wrong. Assume,
- * that the destination is on link.
+ /* When oif is specified, fib_lookup() is called
+ * primarily to determine if the destination is
+ * accessible directly or through a gateway. It also
+ * checks whether there are any traffic restrictions
+ * (blackhole, prohibit, unreachable), or if there's a
+ * routing lookup miss.
*
- * WHY? DW.
- * Because we are allowed to send to iface
- * even if it has NO routes and NO assigned
- * addresses. When oif is specified, routing
- * tables are looked up with only one purpose:
- * to catch if destination is gatewayed, rather than
- * direct. Moreover, if MSG_DONTROUTE is set,
- * we send packet, ignoring both routing tables
- * and ifaddr state. --ANK
- *
- *
- * We could make it even if oif is unknown,
- * likely IPv6, but we do not.
+ * This fallback path is always taken for multicast,
+ * regardless of any restrictions or misses. Non-vrf
+ * unicast does honor restrictions, but falls back if
+ * there's a miss. The destination is assumed on-link
+ * for both.
*/
-
if (fl4->saddr == 0)
fl4->saddr = inet_select_addr(dev_out, 0,
RT_SCOPE_LINK);--
2.47.3