Create parse_ethhdr_vlan() in parsing_helpers.h

This is based on same function from packet-solutions/xdp_vlan02_kern.c
that also extracts VLANs.

It needs to be removed from packet-solutions/xdp_vlan02_kern.c, but
for now its just ifdef defined out-of-code.  Need to run some tests
and look at BPF byte-code to make sure it does the right thing.

The original parse_ethhdr() is implemented by calling parse_ethhdr_vlan()
with NULL argument for stucture to collect IDs into.  The compiler
should remove the parts that are not needed.

Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com>

Author: netoptimizer

common/parsing_helpers.h

@@ -59,6 +59,11 @@ struct icmphdr_common {
 #define VLAN_MAX_DEPTH 2
 #endif
 
+#define VLAN_VID_MASK		0x0fff /* VLAN Identifier */
+struct vlans {
+	__u16 id[VLAN_MAX_DEPTH];
+};
+
 static __always_inline int proto_is_vlan(__u16 h_proto)
 {
 	return !!(h_proto == bpf_htons(ETH_P_8021Q) ||
@@ -70,8 +75,10 @@ static __always_inline int proto_is_vlan(__u16 h_proto)
  * Ethernet header. Thus, caller can look at eth->h_proto to see if this was a
  * VLAN tagged packet.
  */
-static __always_inline int parse_ethhdr(struct hdr_cursor *nh, void *data_end,
-					struct ethhdr **ethhdr)
+static __always_inline int parse_ethhdr_vlan(struct hdr_cursor *nh,
+					     void *data_end,
+					     struct ethhdr **ethhdr,
+					     struct vlans *vlans)
 {
 	struct ethhdr *eth = nh->pos;
 	int hdrsize = sizeof(*eth);
@@ -102,13 +109,25 @@ static __always_inline int parse_ethhdr(struct hdr_cursor *nh, void *data_end,
 			break;
 
 		h_proto = vlh->h_vlan_encapsulated_proto;
+		if (vlans) /* collect VLAN ids */
+			vlans->id[i] =
+				(bpf_ntohs(vlh->h_vlan_TCI) & VLAN_VID_MASK);
+
 		vlh++;
 	}
 
 	nh->pos = vlh;
 	return h_proto; /* network-byte-order */
 }
 
+static __always_inline int parse_ethhdr(struct hdr_cursor *nh,
+					void *data_end,
+					struct ethhdr **ethhdr)
+{
+	/* Expect compiler to remove collect VLAN ids */
+	return parse_ethhdr_vlan(nh, data_end, ethhdr, NULL);
+}
+
 static __always_inline int parse_ip6hdr(struct hdr_cursor *nh,
 					void *data_end,
 					struct ipv6hdr **ip6hdr)

packet-solutions/xdp_vlan02_kern.c

@@ -10,11 +10,14 @@
 #define VLAN_MAX_DEPTH 10
 #include "../common/parsing_helpers.h"
 
+#if 0
 #define VLAN_VID_MASK		0x0fff /* VLAN Identifier */
 struct vlans {
 	__u16 id[VLAN_MAX_DEPTH];
 };
+#endif
 
+#if 0 /* moved to parsing_helpers.h */
 /* Based on parse_ethhdr() */
 static __always_inline int __parse_ethhdr_vlan(struct hdr_cursor *nh,
 					       void *data_end,
@@ -60,6 +63,7 @@ static __always_inline int __parse_ethhdr_vlan(struct hdr_cursor *nh,
 	nh->pos = vlh;
 	return h_proto; /* network-byte-order */
 }
+#endif
 
 SEC("xdp_vlan02")
 int xdp_vlan_02(struct xdp_md *ctx)
@@ -75,7 +79,7 @@ int xdp_vlan_02(struct xdp_md *ctx)
 	struct vlans vlans;
 
 	struct ethhdr *eth;
-	eth_type = __parse_ethhdr_vlan(&nh, data_end, &eth, &vlans);
+	eth_type = parse_ethhdr_vlan(&nh, data_end, &eth, &vlans);
 
 	if (eth_type < 0)
 		return XDP_ABORTED;