The ESP and AH cases in get_ipv6_ext_hdrs() used IPPROTO_FRAGMENT instead
of OFPIEH12_FRAG when checking for out-of-order extension headers, causing
the fragment header to not be recognised as a valid predecessor.

The original code used IPPROTO_FRAGMENT (44) as a bitmask constant where
OFPIEH12_FRAG (1 << 4 = 16) was intended.  IPPROTO_FRAGMENT encodes bits
2, 3 and 5 (OFPIEH12_AUTH | OFPIEH12_DEST | OFPIEH12_ROUTER), but not
bit 4 (OFPIEH12_FRAG).  This caused incorrect OFPIEH12_UNSEQ verdicts in
both the ESP and AH arms: the ESP arm failed to whitelist OFPIEH12_FRAG,
while the AH arm accidentally whitelisted OFPIEH12_AUTH.

With the fix, a packet with two AH headers now also gets OFPIEH12_UNSEQ
in addition to OFPIEH12_UNREP, matching the ESP arm which already sets
UNSEQ on a repeat, which is the intended behavior.

Fixes: 28a3f0601727 ("net: openvswitch: IPv6: Add IPv6 extension header 
support")
Reported-by: Paolo Abeni <[email protected]>
Reviewed-by: Aaron Conole <[email protected]>
Reviewed-by: Ilya Maximets <[email protected]>
Signed-off-by: Eelco Chaudron <[email protected]>

---
v2 changes:
  - Updated commit message as requested by Sashiko.
---
 net/openvswitch/flow.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/net/openvswitch/flow.c b/net/openvswitch/flow.c
index 46c1d66aad8c..868d9fdf3afd 100644
--- a/net/openvswitch/flow.c
+++ b/net/openvswitch/flow.c
@@ -288,7 +288,7 @@ static void get_ipv6_ext_hdrs(struct sk_buff *skb, struct 
ipv6hdr *nh,
                        if (*ext_hdrs & OFPIEH12_ESP)
                                *ext_hdrs |= OFPIEH12_UNREP;
                        if ((*ext_hdrs & ~(OFPIEH12_HOP | OFPIEH12_DEST |
-                                          OFPIEH12_ROUTER | IPPROTO_FRAGMENT |
+                                          OFPIEH12_ROUTER | OFPIEH12_FRAG |
                                           OFPIEH12_AUTH | OFPIEH12_UNREP)) ||
                            dest_options_header_count >= 2) {
                                *ext_hdrs |= OFPIEH12_UNSEQ;
@@ -301,7 +301,7 @@ static void get_ipv6_ext_hdrs(struct sk_buff *skb, struct 
ipv6hdr *nh,
                                *ext_hdrs |= OFPIEH12_UNREP;
                        if ((*ext_hdrs &
                             ~(OFPIEH12_HOP | OFPIEH12_DEST | OFPIEH12_ROUTER |
-                              IPPROTO_FRAGMENT | OFPIEH12_UNREP)) ||
+                              OFPIEH12_FRAG | OFPIEH12_UNREP)) ||
                            dest_options_header_count >= 2) {
                                *ext_hdrs |= OFPIEH12_UNSEQ;
                        }
-- 
2.54.0

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