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SubjectRe: [PATCH v3 net-next 3/7] net: ipv4: use kfree_skb_reason() in ip_rcv_core()
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On 1/28/22 12:33 AM, menglong8.dong@gmail.com wrote:
\> diff --git a/net/ipv4/ip_input.c b/net/ipv4/ip_input.c
> index 3a025c011971..627fad437593 100644
> --- a/net/ipv4/ip_input.c
> +++ b/net/ipv4/ip_input.c
> @@ -436,13 +436,18 @@ static int ip_rcv_finish(struct net *net, struct sock *sk, struct sk_buff *skb)
> static struct sk_buff *ip_rcv_core(struct sk_buff *skb, struct net *net)
> {
> const struct iphdr *iph;
> + int drop_reason;
> u32 len;
>
> + drop_reason = SKB_DROP_REASON_NOT_SPECIFIED;

move this line down, right before:

if (!pskb_may_pull(skb, sizeof(struct iphdr)))
goto inhdr_error;

> +
> /* When the interface is in promisc. mode, drop all the crap
> * that it receives, do not try to analyse it.
> */
> - if (skb->pkt_type == PACKET_OTHERHOST)
> + if (skb->pkt_type == PACKET_OTHERHOST) {
> + drop_reason = SKB_DROP_REASON_OTHERHOST;
> goto drop;
> + }
>
> __IP_UPD_PO_STATS(net, IPSTATS_MIB_IN, skb->len);
>
> @@ -488,6 +493,7 @@ static struct sk_buff *ip_rcv_core(struct sk_buff *skb, struct net *net)
>
> len = ntohs(iph->tot_len);
> if (skb->len < len) {
> + drop_reason = SKB_DROP_REASON_PKT_TOO_SMALL;
> __IP_INC_STATS(net, IPSTATS_MIB_INTRUNCATEDPKTS);
> goto drop;
> } else if (len < (iph->ihl*4))
> @@ -516,11 +522,13 @@ static struct sk_buff *ip_rcv_core(struct sk_buff *skb, struct net *net)
> return skb;
>
> csum_error:
> + drop_reason = SKB_DROP_REASON_IP_CSUM;
> __IP_INC_STATS(net, IPSTATS_MIB_CSUMERRORS);
> inhdr_error:
> + drop_reason = drop_reason ?: SKB_DROP_REASON_IP_INHDR;

That makes assumptions about the value of SKB_DROP_REASON_NOT_SPECIFIED.
Make that line:
if (drop_reason != SKB_DROP_REASON_NOT_SPECIFIED)
drop_reason = SKB_DROP_REASON_IP_INHDR;

> __IP_INC_STATS(net, IPSTATS_MIB_INHDRERRORS);
> drop:
> - kfree_skb(skb);
> + kfree_skb_reason(skb, drop_reason);
> out:
> return NULL;
> }

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