Subject: [PATCH RFC v1 net-next 02/12] netfilter: bridge: Add conntrack double vlan and pppoe

From: Eric Woudstra <[email-masked]>
Date: Sun, 13 Oct 2024 20:54:58 +0200

This adds the capability to conntrack 802.1ad, QinQ, PPPoE and PPPoE-in-Q
packets that are passing a bridge.

Signed-off-by: Eric Woudstra <[email-masked]>
---
 net/bridge/netfilter/nf_conntrack_bridge.c | 86 ++++++++++++++++++----
 1 file changed, 73 insertions(+), 13 deletions(-)

diff --git a/net/bridge/netfilter/nf_conntrack_bridge.c b/net/bridge/netfilter/nf_conntrack_bridge.c
index 816bb0fde718..fb2f79396aa0 100644
--- a/net/bridge/netfilter/nf_conntrack_bridge.c
+++ b/net/bridge/netfilter/nf_conntrack_bridge.c
@@ -241,56 +241,116 @@ static unsigned int nf_ct_bridge_pre(void *priv, struct sk_buff *skb,
 				     const struct nf_hook_state *state)
 {
 	struct nf_hook_state bridge_state = *state;
+	__be16 outer_proto, inner_proto;
 	enum ip_conntrack_info ctinfo;
+	int ret, offset = 0;
 	struct nf_conn *ct;
-	u32 len;
-	int ret;
+	u32 len, data_len;
 
 	ct = nf_ct_get(skb, &ctinfo);
 	if ((ct && !nf_ct_is_template(ct)) ||
 	    ctinfo == IP_CT_UNTRACKED)
 		return NF_ACCEPT;
 
+	switch (skb->protocol) {
+	case htons(ETH_P_PPP_SES):
+		struct ppp_hdr {
+			struct pppoe_hdr hdr;
+			__be16 proto;
+		} *ph = (struct ppp_hdr *)(skb->data);
+
+		data_len = ntohs(ph->hdr.length) - 2;
+		offset = PPPOE_SES_HLEN;
+		outer_proto = skb->protocol;
+		switch (ph->proto) {
+		case htons(PPP_IP):
+			inner_proto = htons(ETH_P_IP);
+			break;
+		case htons(PPP_IPV6):
+			inner_proto = htons(ETH_P_IPV6);
+			break;
+		default:
+			return NF_ACCEPT;
+		}
+		break;
+	case htons(ETH_P_8021Q):
+		struct vlan_hdr *vhdr = (struct vlan_hdr *)(skb->data);
+
+		data_len = 0xffffffff;
+		offset = VLAN_HLEN;
+		outer_proto = skb->protocol;
+		inner_proto = vhdr->h_vlan_encapsulated_proto;
+		break;
+	default:
+		data_len = 0xffffffff;
+		break;
+	}
+
+	if (offset) {
+		switch (inner_proto) {
+		case htons(ETH_P_IP):
+		case htons(ETH_P_IPV6):
+			if (!pskb_may_pull(skb, offset))
+				return NF_ACCEPT;
+			skb_pull_rcsum(skb, offset);
+			skb_reset_network_header(skb);
+			skb->protocol = inner_proto;
+			break;
+		default:
+			return NF_ACCEPT;
+		}
+	}
+
+	ret = NF_ACCEPT;
 	switch (skb->protocol) {
 	case htons(ETH_P_IP):
 		if (!pskb_may_pull(skb, sizeof(struct iphdr)))
-			return NF_ACCEPT;
+			goto do_not_track;
 
 		len = skb_ip_totlen(skb);
+		if (data_len < len)
+			len = data_len;
 		if (pskb_trim_rcsum(skb, len))
-			return NF_ACCEPT;
+			goto do_not_track;
 
 		if (nf_ct_br_ip_check(skb))
-			return NF_ACCEPT;
+			goto do_not_track;
 
 		bridge_state.pf = NFPROTO_IPV4;
 		ret = nf_ct_br_defrag4(skb, &bridge_state);
 		break;
 	case htons(ETH_P_IPV6):
 		if (!pskb_may_pull(skb, sizeof(struct ipv6hdr)))
-			return NF_ACCEPT;
+			goto do_not_track;
 
 		len = sizeof(struct ipv6hdr) + ntohs(ipv6_hdr(skb)->payload_len);
+		if (data_len < len)
+			len = data_len;
 		if (pskb_trim_rcsum(skb, len))
-			return NF_ACCEPT;
+			goto do_not_track;
 
 		if (nf_ct_br_ipv6_check(skb))
-			return NF_ACCEPT;
+			goto do_not_track;
 
 		bridge_state.pf = NFPROTO_IPV6;
 		ret = nf_ct_br_defrag6(skb, &bridge_state);
 		break;
 	default:
 		nf_ct_set(skb, NULL, IP_CT_UNTRACKED);
-		return NF_ACCEPT;
+		goto do_not_track;
 	}
 
-	if (ret != NF_ACCEPT)
-		return ret;
+	if (ret == NF_ACCEPT)
+		ret = nf_conntrack_in(skb, &bridge_state);
 
-	return nf_conntrack_in(skb, &bridge_state);
+do_not_track:
+	if (offset) {
+		skb_push_rcsum(skb, offset);
+		skb_reset_network_header(skb);
+		skb->protocol = outer_proto;
+	}
+	return ret;
 }
-
 static unsigned int nf_ct_bridge_in(void *priv, struct sk_buff *skb,
 				    const struct nf_hook_state *state)
 {
-- 
2.45.2