linux-kernel - [PATCH net-next 6/9] net: ipv6: remove redundant statistics in ipv6_hop

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Date:   Wed, 13 Apr 2022 16:15:57 +0800
From:   menglong8.dong@...il.com
To:     dsahern@...nel.org
Cc:     rostedt@...dmis.org, mingo@...hat.com, davem@...emloft.net,
        yoshfuji@...ux-ipv6.org, kuba@...nel.org, pabeni@...hat.com,
        benbjiang@...cent.com, flyingpeng@...cent.com,
        imagedong@...cent.com, edumazet@...gle.com, kafai@...com,
        talalahmad@...gle.com, keescook@...omium.org,
        mengensun@...cent.com, dongli.zhang@...cle.com,
        linux-kernel@...r.kernel.org, netdev@...r.kernel.org
Subject: [PATCH net-next 6/9] net: ipv6: remove redundant statistics in ipv6_hop_jumbo()

From: Menglong Dong <imagedong@...cent.com>

There are two call chains for ipv6_hop_jumbo(). The first one is:

ipv6_destopt_rcv() -> ip6_parse_tlv() -> ipv6_hop_jumbo()

On this call chain, the drop statistics will be done in
ipv6_destopt_rcv() with 'IPSTATS_MIB_INHDRERRORS' if ipv6_hop_jumbo()
returns false.

The second call chain is:

ip6_rcv_core() -> ipv6_parse_hopopts() -> ip6_parse_tlv()

And the drop statistics will also be done in ip6_rcv_core() with
'IPSTATS_MIB_INHDRERRORS' if ipv6_hop_jumbo() returns false.

Therefore, the statistics in ipv6_hop_jumbo() is redundant, which
means the drop is counted twice. The statistics in ipv6_hop_jumbo()
is almost the same as the outside, except the
'IPSTATS_MIB_INTRUNCATEDPKTS', which seems that we have to ignore it.

Signed-off-by: Menglong Dong <imagedong@...cent.com>
Reviewed-by: Jiang Biao <benbjiang@...cent.com>
Reviewed-by: Hao Peng <flyingpeng@...cent.com>
---
 net/ipv6/exthdrs.c | 9 +--------
 1 file changed, 1 insertion(+), 8 deletions(-)

diff --git a/net/ipv6/exthdrs.c b/net/ipv6/exthdrs.c
index 658d5eabaf7e..31318ee62d29 100644
--- a/net/ipv6/exthdrs.c
+++ b/net/ipv6/exthdrs.c
@@ -997,33 +997,26 @@ static bool ipv6_hop_ioam(struct sk_buff *skb, int optoff)
 static bool ipv6_hop_jumbo(struct sk_buff *skb, int optoff)
 {
 	const unsigned char *nh = skb_network_header(skb);
-	struct inet6_dev *idev = __in6_dev_get_safely(skb->dev);
-	struct net *net = ipv6_skb_net(skb);
 	u32 pkt_len;
 
 	if (nh[optoff + 1] != 4 || (optoff & 3) != 2) {
 		net_dbg_ratelimited("ipv6_hop_jumbo: wrong jumbo opt length/alignment %d\n",
 				    nh[optoff+1]);
-		__IP6_INC_STATS(net, idev, IPSTATS_MIB_INHDRERRORS);
 		goto drop;
 	}
 
 	pkt_len = ntohl(*(__be32 *)(nh + optoff + 2));
 	if (pkt_len <= IPV6_MAXPLEN) {
-		__IP6_INC_STATS(net, idev, IPSTATS_MIB_INHDRERRORS);
 		icmpv6_param_prob(skb, ICMPV6_HDR_FIELD, optoff+2);
 		return false;
 	}
 	if (ipv6_hdr(skb)->payload_len) {
-		__IP6_INC_STATS(net, idev, IPSTATS_MIB_INHDRERRORS);
 		icmpv6_param_prob(skb, ICMPV6_HDR_FIELD, optoff);
 		return false;
 	}
 
-	if (pkt_len > skb->len - sizeof(struct ipv6hdr)) {
-		__IP6_INC_STATS(net, idev, IPSTATS_MIB_INTRUNCATEDPKTS);
+	if (pkt_len > skb->len - sizeof(struct ipv6hdr))
 		goto drop;
-	}
 
 	if (pskb_trim_rcsum(skb, pkt_len + sizeof(struct ipv6hdr)))
 		goto drop;
-- 
2.35.1