On 1/24/22 6:15 AM, menglong8.dong@xxxxxxxxx wrote:
> diff --git a/net/ipv4/ip_input.c b/net/ipv4/ip_input.c
> index ab9bee4bbf0a..77bb9ddc441b 100644
> --- a/net/ipv4/ip_input.c
> +++ b/net/ipv4/ip_input.c
> @@ -318,8 +318,10 @@ static int ip_rcv_finish_core(struct net *net, struct sock *sk,
> {
> const struct iphdr *iph = ip_hdr(skb);
> int (*edemux)(struct sk_buff *skb);
> + int err, drop_reason;
> struct rtable *rt;
> - int err;
> +
> + drop_reason = SKB_DROP_REASON_NOT_SPECIFIED;
>
> if (ip_can_use_hint(skb, iph, hint)) {
> err = ip_route_use_hint(skb, iph->daddr, iph->saddr, iph->tos,
> @@ -339,8 +341,10 @@ static int ip_rcv_finish_core(struct net *net, struct sock *sk,
> if (ipprot && (edemux = READ_ONCE(ipprot->early_demux))) {
> err = INDIRECT_CALL_2(edemux, tcp_v4_early_demux,
> udp_v4_early_demux, skb);
> - if (unlikely(err))
> + if (unlikely(err)) {
> + drop_reason = SKB_DROP_REASON_EARLY_DEMUX;
is there really value in this one? You ignore the error case from
ip_route_use_hint which is a similar, highly unlikely error path so why
care about this one? The only failure case is ip_mc_validate_source from
udp_v4_early_demux and 'early demux' drops really mean nothing to the user.
> goto drop_error;
> + }
> /* must reload iph, skb->head might have changed */
> iph = ip_hdr(skb);
> }
> @@ -353,8 +357,10 @@ static int ip_rcv_finish_core(struct net *net, struct sock *sk,
> if (!skb_valid_dst(skb)) {
> err = ip_route_input_noref(skb, iph->daddr, iph->saddr,
> iph->tos, dev);
> - if (unlikely(err))
> + if (unlikely(err)) {
> + drop_reason = SKB_DROP_REASON_IP_ROUTE_INPUT;
The reason codes should be meaningful to users and not derived from a
code path. What does SKB_DROP_REASON_IP_ROUTE_INPUT mean as a failure?
> goto drop_error;
> + }
> }
>
> #ifdef CONFIG_IP_ROUTE_CLASSID
