static inline bool flow_dissector()

in bpf/sockex2_kern.c [100:186]

• 75 lines of code
• 16 McCabe index (conditional complexity)

static inline bool flow_dissector(struct __sk_buff *skb,
				  struct flow_key_record *flow)
{
	__u64 nhoff = ETH_HLEN;
	__u64 ip_proto;
	__u64 proto = load_half(skb, 12);
	int poff;

	if (proto == ETH_P_8021AD) {
		proto = load_half(skb, nhoff + offsetof(struct vlan_hdr,
							h_vlan_encapsulated_proto));
		nhoff += sizeof(struct vlan_hdr);
	}

	if (proto == ETH_P_8021Q) {
		proto = load_half(skb, nhoff + offsetof(struct vlan_hdr,
							h_vlan_encapsulated_proto));
		nhoff += sizeof(struct vlan_hdr);
	}

	if (likely(proto == ETH_P_IP))
		nhoff = parse_ip(skb, nhoff, &ip_proto, flow);
	else if (proto == ETH_P_IPV6)
		nhoff = parse_ipv6(skb, nhoff, &ip_proto, flow);
	else
		return false;

	switch (ip_proto) {
	case IPPROTO_GRE: {
		struct gre_hdr {
			__be16 flags;
			__be16 proto;
		};

		__u64 gre_flags = load_half(skb,
					    nhoff + offsetof(struct gre_hdr, flags));
		__u64 gre_proto = load_half(skb,
					    nhoff + offsetof(struct gre_hdr, proto));

		if (gre_flags & (GRE_VERSION|GRE_ROUTING))
			break;

		proto = gre_proto;
		nhoff += 4;
		if (gre_flags & GRE_CSUM)
			nhoff += 4;
		if (gre_flags & GRE_KEY)
			nhoff += 4;
		if (gre_flags & GRE_SEQ)
			nhoff += 4;

		if (proto == ETH_P_8021Q) {
			proto = load_half(skb,
					  nhoff + offsetof(struct vlan_hdr,
							   h_vlan_encapsulated_proto));
			nhoff += sizeof(struct vlan_hdr);
		}

		if (proto == ETH_P_IP)
			nhoff = parse_ip(skb, nhoff, &ip_proto, flow);
		else if (proto == ETH_P_IPV6)
			nhoff = parse_ipv6(skb, nhoff, &ip_proto, flow);
		else
			return false;
		break;
	}
	case IPPROTO_IPIP:
		nhoff = parse_ip(skb, nhoff, &ip_proto, flow);
		break;
	case IPPROTO_IPV6:
		nhoff = parse_ipv6(skb, nhoff, &ip_proto, flow);
		break;
	default:
		break;
	}

	flow->ip_proto = ip_proto;
	poff = proto_ports_offset(ip_proto);
	if (poff >= 0) {
		nhoff += poff;
		flow->ports = load_word(skb, nhoff);
	}

	flow->thoff = (__u16) nhoff;

	return true;
}