[PATCH nf-next v3 2/3] netfilter: bridge: pass L2 header and VLAN as netlink attributes in queues to userspace

[Stephane Bryant <stephane.ml.bryant@gmail.com>]

From: stephane <stephane.ml.bryant@gmail.com>

-this creates 2 netlink attribute NLQA_VLAN and NLQA_L2HDR
-these are filled up for the PF_BRIDGE family on the way to userspace

Signed-off-by: Stephane Bryant <stephane.ml.bryant@gmail.com>
---
 include/uapi/linux/netfilter/nfnetlink_queue.h |  7 ++++
 net/netfilter/nfnetlink_queue.c                | 53 ++++++++++++++++++++++++++
 2 files changed, 60 insertions(+)

diff --git a/include/uapi/linux/netfilter/nfnetlink_queue.h b/include/uapi/linux/netfilter/nfnetlink_queue.h
index b67a853..211fcdc 100644
--- a/include/uapi/linux/netfilter/nfnetlink_queue.h
+++ b/include/uapi/linux/netfilter/nfnetlink_queue.h
@@ -30,6 +30,11 @@ struct nfqnl_msg_packet_timestamp {
 	__aligned_be64	usec;
 };
 
+struct nfqnl_msg_vlan {
+	__be16                  proto;
+	__u16                   tci;
+} __attribute__ ((packed));
+
 enum nfqnl_attr_type {
 	NFQA_UNSPEC,
 	NFQA_PACKET_HDR,
@@ -50,6 +55,8 @@ enum nfqnl_attr_type {
 	NFQA_UID,			/* __u32 sk uid */
 	NFQA_GID,			/* __u32 sk gid */
 	NFQA_SECCTX,			/* security context string */
+	NFQA_VLAN,                      /* packet vlan info */
+	NFQA_L2HDR,                     /* full L2 header */
 
 	__NFQA_MAX
 };
diff --git a/net/netfilter/nfnetlink_queue.c b/net/netfilter/nfnetlink_queue.c
index 1d39365..b40cdb4 100644
--- a/net/netfilter/nfnetlink_queue.c
+++ b/net/netfilter/nfnetlink_queue.c
@@ -295,6 +295,54 @@ static u32 nfqnl_get_sk_secctx(struct sk_buff *skb, char **secdata)
 	return seclen;
 }
 
+static u32 nfqnl_get_bridge_nla_len(struct nf_queue_entry *entry)
+{
+	u32 nlalen = 0;
+	struct sk_buff *entskb = entry->skb;
+
+	if ((entry->state.pf != PF_BRIDGE) || (!skb_mac_header_was_set(entskb)))
+		return 0;
+
+	if (skb_vlan_tag_present(entskb))
+		nlalen += nla_total_size(sizeof(struct nfqnl_msg_vlan));
+
+	if (entskb->network_header > entskb->mac_header)
+		nlalen += nla_total_size((entskb->network_header -
+					  entskb->mac_header));
+
+	return nlalen;
+}
+
+static int nfqnl_put_bridge_nla(struct nf_queue_entry *entry,
+				struct sk_buff *skb)
+{
+	struct sk_buff *entskb = entry->skb;
+
+	if ((entry->state.pf != PF_BRIDGE) || (!skb_mac_header_was_set(entskb)))
+		return 0;
+
+	if (skb_vlan_tag_present(entskb)) {
+		struct nfqnl_msg_vlan pvlan;
+
+		pvlan.tci = entskb->vlan_tci;
+		pvlan.proto = entskb->vlan_proto;
+		if (nla_put(skb, NFQA_VLAN, sizeof(pvlan), &pvlan))
+			goto nla_put_failure;
+	}
+
+	if (entskb->mac_header < entskb->network_header) {
+		int len = (int)(entskb->network_header - entskb->mac_header);
+
+		if (nla_put(skb, NFQA_L2HDR, len, skb_mac_header(entskb)))
+			goto nla_put_failure;
+	}
+
+	return 0;
+
+nla_put_failure:
+	return -1;
+}
+
 static struct sk_buff *
 nfqnl_build_packet_message(struct net *net, struct nfqnl_instance *queue,
 			   struct nf_queue_entry *entry,
@@ -334,6 +382,8 @@ nfqnl_build_packet_message(struct net *net, struct nfqnl_instance *queue,
 	if (entskb->tstamp.tv64)
 		size += nla_total_size(sizeof(struct nfqnl_msg_packet_timestamp));
 
+	size += nfqnl_get_bridge_nla_len(entry);
+
 	if (entry->state.hook <= NF_INET_FORWARD ||
 	   (entry->state.hook == NF_INET_POST_ROUTING && entskb->sk == NULL))
 		csum_verify = !skb_csum_unnecessary(entskb);
@@ -499,6 +549,9 @@ nfqnl_build_packet_message(struct net *net, struct nfqnl_instance *queue,
 		}
 	}
 
+	if (nfqnl_put_bridge_nla(entry, skb))
+		goto nla_put_failure;
+
 	if (entskb->tstamp.tv64) {
 		struct nfqnl_msg_packet_timestamp ts;
 		struct timespec64 kts = ktime_to_timespec64(skb->tstamp);
-- 
2.1.4