datapath: Derive IP protocol number for IPv6 later frags

Upstream commit:
    commit fa642f08839bf2ff35b2f6c6a6c062aee8121ba8
    Author: Yi-Hung Wei <yihung.wei@gmail.com>
    Date:   Tue Sep 4 15:33:41 2018 -0700

    openvswitch: Derive IP protocol number for IPv6 later frags

    Currently, OVS only parses the IP protocol number for the first
    IPv6 fragment, but sets the IP protocol number for the later fragments
    to be NEXTHDF_FRAGMENT.  This patch tries to derive the IP protocol
    number for the IPV6 later frags so that we can match that.

    Signed-off-by: Yi-Hung Wei <yihung.wei@gmail.com>
    Acked-by: Pravin B Shelar <pshelar@ovn.org>
    Signed-off-by: David S. Miller <davem@davemloft.net>

CC: Yi-Hung Wei <yihung.wei@gmail.com>
Signed-off-by: Greg Rose <gvrose8192@gmail.com>
Signed-off-by: Ben Pfaff <blp@ovn.org>

datapath/flow.c

@@ -254,21 +254,18 @@ static bool icmphdr_ok(struct sk_buff *skb)
 
 static int parse_ipv6hdr(struct sk_buff *skb, struct sw_flow_key *key)
 {
+	unsigned short frag_off;
+	unsigned int payload_ofs = 0;
 	unsigned int nh_ofs = skb_network_offset(skb);
 	unsigned int nh_len;
-	int payload_ofs;
 	struct ipv6hdr *nh;
-	uint8_t nexthdr;
-	__be16 frag_off;
-	int err;
+	int err, nexthdr, flags = 0;
 
 	err = check_header(skb, nh_ofs + sizeof(*nh));
 	if (unlikely(err))
 		return err;
 
 	nh = ipv6_hdr(skb);
-	nexthdr = nh->nexthdr;
-	payload_ofs = (u8 *)(nh + 1) - skb->data;
 
 	key->ip.proto = NEXTHDR_NONE;
 	key->ip.tos = ipv6_get_dsfield(nh);
@@ -277,22 +274,21 @@ static int parse_ipv6hdr(struct sk_buff *skb, struct sw_flow_key *key)
 	key->ipv6.addr.src = nh->saddr;
 	key->ipv6.addr.dst = nh->daddr;
 
-	payload_ofs = ipv6_skip_exthdr(skb, payload_ofs, &nexthdr, &frag_off);
-
-	if (frag_off) {
-		if (frag_off & htons(~0x7))
+	nexthdr = ipv6_find_hdr(skb, &payload_ofs, -1, &frag_off, &flags);
+	if (flags & IP6_FH_F_FRAG) {
+		if (frag_off)
 			key->ip.frag = OVS_FRAG_TYPE_LATER;
 		else
 			key->ip.frag = OVS_FRAG_TYPE_FIRST;
 	} else {
 		key->ip.frag = OVS_FRAG_TYPE_NONE;
 	}
 
-	/* Delayed handling of error in ipv6_skip_exthdr() as it
-	 * always sets frag_off to a valid value which may be
+	/* Delayed handling of error in ipv6_find_hdr() as it
+	 * always sets flags and frag_off to a valid value which may be
 	 * used to set key->ip.frag above.
 	 */
-	if (unlikely(payload_ofs < 0))
+	if (unlikely(nexthdr < 0))
 		return -EPROTO;
 
 	nh_len = payload_ofs - nh_ofs;