flow_dissector: add support for dst, hop-by-hop and routing ext hdrs

If dst, hop-by-hop or routing extension headers are present determine
length of the options and skip over them in flow dissection.
Signed-off-by: Tom Herbert <tom@herbertland.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/core/flow_dissector.c

@@ -327,6 +327,7 @@ bool __skb_flow_dissect(const struct sk_buff *skb,
 		return false;
 	}
 
+ip_proto_again:
 	switch (ip_proto) {
 	case IPPROTO_GRE: {
 		struct gre_hdr {
@@ -383,6 +384,22 @@ bool __skb_flow_dissect(const struct sk_buff *skb,
 		}
 		goto again;
 	}
+	case NEXTHDR_HOP:
+	case NEXTHDR_ROUTING:
+	case NEXTHDR_DEST: {
+		u8 _opthdr[2], *opthdr;
+
+		if (proto != htons(ETH_P_IPV6))
+			break;
+
+		opthdr = __skb_header_pointer(skb, nhoff, sizeof(_opthdr),
+					      data, hlen, &_opthdr);
+
+		ip_proto = _opthdr[0];
+		nhoff += (_opthdr[1] + 1) << 3;
+
+		goto ip_proto_again;
+	}
 	case IPPROTO_IPIP:
 		proto = htons(ETH_P_IP);
 		goto ip;