netdev - [PATCH net-next 09/10] netfilter: get ipv6 pktlen properly in length

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Date:   Fri, 13 Jan 2023 22:31:33 -0500
From:   Xin Long <lucien.xin@...il.com>
To:     network dev <netdev@...r.kernel.org>
Cc:     davem@...emloft.net, kuba@...nel.org,
        Eric Dumazet <edumazet@...gle.com>,
        Paolo Abeni <pabeni@...hat.com>,
        David Ahern <dsahern@...il.com>,
        Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>,
        Pravin B Shelar <pshelar@....org>,
        Jamal Hadi Salim <jhs@...atatu.com>,
        Cong Wang <xiyou.wangcong@...il.com>,
        Jiri Pirko <jiri@...nulli.us>,
        Pablo Neira Ayuso <pablo@...filter.org>,
        Florian Westphal <fw@...len.de>,
        Marcelo Ricardo Leitner <marcelo.leitner@...il.com>,
        Ilya Maximets <i.maximets@....org>,
        Aaron Conole <aconole@...hat.com>,
        Roopa Prabhu <roopa@...dia.com>,
        Nikolay Aleksandrov <razor@...ckwall.org>,
        Mahesh Bandewar <maheshb@...gle.com>,
        Paul Moore <paul@...l-moore.com>,
        Guillaume Nault <gnault@...hat.com>
Subject: [PATCH net-next 09/10] netfilter: get ipv6 pktlen properly in length_mt6

For IPv6 jumbogram packets, the packet size is bigger than 65535,
it's not right to get it from payload_len and save it to an u16
variable.

This patch only fixes it for IPv6 BIG TCP packets, so instead of
parsing IPV6_TLV_JUMBO exthdr, which is quite some work, it only
gets the pktlen via 'skb->len - skb_network_offset(skb)' when
skb_is_gso_v6() and saves it to an u32 variable, similar to IPv4
BIG TCP packets.

This fix will also help us add selftest for IPv6 BIG TCP in the
following patch.

Signed-off-by: Xin Long <lucien.xin@...il.com>
---
 include/linux/ipv6.h      | 9 +++++++++
 net/netfilter/xt_length.c | 3 +--
 2 files changed, 10 insertions(+), 2 deletions(-)

diff --git a/include/linux/ipv6.h b/include/linux/ipv6.h
index 37dfdcfcdd54..b8edd6c599eb 100644
--- a/include/linux/ipv6.h
+++ b/include/linux/ipv6.h
@@ -175,6 +175,15 @@ static inline bool inet6_is_jumbogram(const struct sk_buff *skb)
 	return !!(IP6CB(skb)->flags & IP6SKB_JUMBOGRAM);
 }
 
+static inline unsigned int skb_ipv6_totlen(const struct sk_buff *skb)
+{
+	u32 pl = ntohs(ipv6_hdr(skb)->payload_len);
+
+	return pl ? pl + sizeof(struct ipv6hdr)
+		  : (skb_is_gso_v6(skb) ? skb->len - skb_network_offset(skb)
+					: pl + sizeof(struct ipv6hdr));
+}
+
 /* can not be used in TCP layer after tcp_v6_fill_cb */
 static inline int inet6_sdif(const struct sk_buff *skb)
 {
diff --git a/net/netfilter/xt_length.c b/net/netfilter/xt_length.c
index b3d623a52885..61518ec05c6e 100644
--- a/net/netfilter/xt_length.c
+++ b/net/netfilter/xt_length.c
@@ -30,8 +30,7 @@ static bool
 length_mt6(const struct sk_buff *skb, struct xt_action_param *par)
 {
 	const struct xt_length_info *info = par->matchinfo;
-	const u_int16_t pktlen = ntohs(ipv6_hdr(skb)->payload_len) +
-				 sizeof(struct ipv6hdr);
+	u32 pktlen = skb_ipv6_totlen(skb);
 
 	return (pktlen >= info->min && pktlen <= info->max) ^ info->invert;
 }
-- 
2.31.1