netdev - [PATCH v17 nf-next 4/4] netfilter: nft_chain_filter: Add bridge double vlan and pppoe

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Message-ID: <20251109192427.617142-5-ericwouds@gmail.com>
Date: Sun,  9 Nov 2025 20:24:27 +0100
From: Eric Woudstra <ericwouds@...il.com>
To: Pablo Neira Ayuso <pablo@...filter.org>,
	Jozsef Kadlecsik <kadlec@...filter.org>,
	Florian Westphal <fw@...len.de>,
	Phil Sutter <phil@....cc>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>,
	Paolo Abeni <pabeni@...hat.com>,
	Simon Horman <horms@...nel.org>,
	Nikolay Aleksandrov <razor@...ckwall.org>,
	Ido Schimmel <idosch@...dia.com>
Cc: netfilter-devel@...r.kernel.org,
	netdev@...r.kernel.org,
	bridge@...ts.linux.dev,
	Eric Woudstra <ericwouds@...il.com>
Subject: [PATCH v17 nf-next 4/4] netfilter: nft_chain_filter: Add bridge double vlan and pppoe

In nft_do_chain_bridge() pktinfo is only fully populated for plain packets
and packets encapsulated in single 802.1q or 802.1ad.

When implementing the software bridge-fastpath and testing all possible
encapulations, there can be more encapsulations:

The packet could (also) be encapsulated in PPPoE, or the packet could be
encapsulated in an inner 802.1q, combined with an outer 802.1ad or 802.1q
encapsulation.

nft_flow_offload_eval() also examines the L4 header, with the L4 protocol
known from the conntrack-tuplehash. To access the header it uses
nft_thoff(), but for these packets it returns zero.

Introduce nft_set_bridge_pktinfo() to help populate pktinfo with the
offsets.

Signed-off-by: Eric Woudstra <ericwouds@...il.com>
---
 net/netfilter/nft_chain_filter.c | 55 +++++++++++++++++++++++++++++---
 1 file changed, 51 insertions(+), 4 deletions(-)

diff --git a/net/netfilter/nft_chain_filter.c b/net/netfilter/nft_chain_filter.c
index d4d5eadaba9c..082b10e9e853 100644
--- a/net/netfilter/nft_chain_filter.c
+++ b/net/netfilter/nft_chain_filter.c
@@ -227,21 +227,68 @@ static inline void nft_chain_filter_inet_fini(void) {}
 #endif /* CONFIG_NF_TABLES_IPV6 */
 
 #if IS_ENABLED(CONFIG_NF_TABLES_BRIDGE)
+static int nft_set_bridge_pktinfo(struct nft_pktinfo *pkt, struct sk_buff *skb,
+				  const struct nf_hook_state *state,
+				  __be16 *proto)
+{
+	nft_set_pktinfo(pkt, skb, state);
+
+	switch (*proto) {
+	case htons(ETH_P_PPP_SES): {
+		struct ppp_hdr {
+			struct pppoe_hdr hdr;
+			__be16 proto;
+		} *ph;
+
+		if (!pskb_may_pull(skb, PPPOE_SES_HLEN)) {
+			*proto = 0;
+			return -1;
+		}
+		ph = (struct ppp_hdr *)(skb->data);
+		switch (ph->proto) {
+		case htons(PPP_IP):
+			*proto = htons(ETH_P_IP);
+			return PPPOE_SES_HLEN;
+		case htons(PPP_IPV6):
+			*proto = htons(ETH_P_IPV6);
+			return PPPOE_SES_HLEN;
+		}
+		break;
+	}
+	case htons(ETH_P_8021Q): {
+		struct vlan_hdr *vhdr;
+
+		if (!pskb_may_pull(skb, VLAN_HLEN)) {
+			*proto = 0;
+			return -1;
+		}
+		vhdr = (struct vlan_hdr *)(skb->data);
+		*proto = vhdr->h_vlan_encapsulated_proto;
+		return VLAN_HLEN;
+	}
+	}
+	return 0;
+}
+
 static unsigned int
 nft_do_chain_bridge(void *priv,
 		    struct sk_buff *skb,
 		    const struct nf_hook_state *state)
 {
 	struct nft_pktinfo pkt;
+	__be16 proto;
+	int offset;
 
-	nft_set_pktinfo(&pkt, skb, state);
+	proto = eth_hdr(skb)->h_proto;
+
+	offset = nft_set_bridge_pktinfo(&pkt, skb, state, &proto);
 
-	switch (eth_hdr(skb)->h_proto) {
+	switch (proto) {
 	case htons(ETH_P_IP):
-		nft_set_pktinfo_ipv4_validate(&pkt, 0);
+		nft_set_pktinfo_ipv4_validate(&pkt, offset);
 		break;
 	case htons(ETH_P_IPV6):
-		nft_set_pktinfo_ipv6_validate(&pkt, 0);
+		nft_set_pktinfo_ipv6_validate(&pkt, offset);
 		break;
 	default:
 		nft_set_pktinfo_unspec(&pkt);
-- 
2.50.0