Re: [PATCH RESEND net-next v4 9/9] net: ip: make ip_route_use_hint() return drop reasons

On Tue, Nov 5, 2024 at 7:28 PM Paolo Abeni [off-list ref] wrote:

On 10/30/24 02:41, Menglong Dong wrote:

quoted

diff --git a/net/ipv4/route.c b/net/ipv4/route.c
index e248e5577d0e..7f969c865c81 100644
--- a/net/ipv4/route.c
+++ b/net/ipv4/route.c

@@ -2142,28 +2142,34 @@ ip_mkroute_input(struct sk_buff *skb, struct fib_result *res,
  * assuming daddr is valid and the destination is not a local broadcast one.
  * Uses the provided hint instead of performing a route lookup.
  */
-int ip_route_use_hint(struct sk_buff *skb, __be32 daddr, __be32 saddr,
-                   dscp_t dscp, struct net_device *dev,
-                   const struct sk_buff *hint)
+enum skb_drop_reason
+ip_route_use_hint(struct sk_buff *skb, __be32 daddr, __be32 saddr,
+               dscp_t dscp, struct net_device *dev,
+               const struct sk_buff *hint)
 {
+     enum skb_drop_reason reason = SKB_DROP_REASON_NOT_SPECIFIED;
      struct in_device *in_dev = __in_dev_get_rcu(dev);
      struct rtable *rt = skb_rtable(hint);
      struct net *net = dev_net(dev);
-     enum skb_drop_reason reason;
-     int err = -EINVAL;
      u32 tag = 0;

      if (!in_dev)
-             return -EINVAL;
+             return reason;

-     if (ipv4_is_multicast(saddr) || ipv4_is_lbcast(saddr))
+     if (ipv4_is_multicast(saddr) || ipv4_is_lbcast(saddr)) {
+             reason = SKB_DROP_REASON_IP_INVALID_SOURCE;
              goto martian_source;
+     }

-     if (ipv4_is_zeronet(saddr))
+     if (ipv4_is_zeronet(saddr)) {
+             reason = SKB_DROP_REASON_IP_INVALID_SOURCE;
              goto martian_source;
+     }

-     if (ipv4_is_loopback(saddr) && !IN_DEV_NET_ROUTE_LOCALNET(in_dev, net))
+     if (ipv4_is_loopback(saddr) && !IN_DEV_NET_ROUTE_LOCALNET(in_dev, net)) {
+             reason = IP_LOCALNET;
              goto martian_source;
+     }

      if (rt->rt_type != RTN_LOCAL)
              goto skip_validate_source;

Please explicitly replace also the

        return 0;

with

        return SKB_NOT_DROPPED_YET;

So that is clear the drop reason is always specified.

Okay!

Thanks!
Menglong Dong

Thanks,

Paolo