netdev - [PATCH v2] openvswitch: retain parsed IPv6 header fields in flow on error skipping extension headers

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Message-Id: <1440806541-22729-1-git-send-email-simon.horman@netronome.com>
Date:	Sat, 29 Aug 2015 09:02:21 +0900
From:	Simon Horman <simon.horman@...ronome.com>
To:	Pravin Shelar <pshelar@...ira.com>,
	David Miller <davem@...emloft.net>
Cc:	netdev@...r.kernel.org, dev@...nvswitch.org,
	Simon Horman <simon.horman@...ronome.com>
Subject: [PATCH v2] openvswitch: retain parsed IPv6 header fields in flow on error skipping extension headers

When an error occurs skipping IPv6 extension headers retain the already
parsed IP protocol and IPv6 addresses in the flow. Also assume that the
packet is not a fragment in the absence of information to the contrary;
that is always use the frag_off value set by ipv6_skip_exthdr().

This allows matching on the IP protocol and IPv6 addresses of packets
with malformed extension headers.

Signed-off-by: Simon Horman <simon.horman@...ronome.com>

---

v2
* As suggested by Pravin Shelar
  - Use new errno for the case handled by this patch in order
    to retain the old behaviour if the call to check_header()
    in parse_ipv6hdr() returns -EINVAL, which it may.
* Dropped RFC from prefix

* Some consideration should be given to unwanted side effects of this patch
  as it affects the handling of malformed packets.
---
 net/openvswitch/flow.c | 21 +++++++++++++++------
 1 file changed, 15 insertions(+), 6 deletions(-)

diff --git a/net/openvswitch/flow.c b/net/openvswitch/flow.c
index 5a3195e538ce..daf914ec58d0 100644
--- a/net/openvswitch/flow.c
+++ b/net/openvswitch/flow.c
@@ -272,8 +272,6 @@ static int parse_ipv6hdr(struct sk_buff *skb, struct sw_flow_key *key)
 	key->ipv6.addr.dst = nh->daddr;
 
 	payload_ofs = ipv6_skip_exthdr(skb, payload_ofs, &nexthdr, &frag_off);
-	if (unlikely(payload_ofs < 0))
-		return -EINVAL;
 
 	if (frag_off) {
 		if (frag_off & htons(~0x7))
@@ -284,6 +282,13 @@ static int parse_ipv6hdr(struct sk_buff *skb, struct sw_flow_key *key)
 		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
+	 * used to set key->ip.frag above.
+	 */
+	if (unlikely(payload_ofs < 0))
+		return -EPROTO;
+
 	nh_len = payload_ofs - nh_ofs;
 	skb_set_transport_header(skb, nh_ofs + nh_len);
 	key->ip.proto = nexthdr;
@@ -623,12 +628,16 @@ static int key_extract(struct sk_buff *skb, struct sw_flow_key *key)
 
 		nh_len = parse_ipv6hdr(skb, key);
 		if (unlikely(nh_len < 0)) {
-			memset(&key->ip, 0, sizeof(key->ip));
-			memset(&key->ipv6.addr, 0, sizeof(key->ipv6.addr));
-			if (nh_len == -EINVAL) {
+			switch (nh_len) {
+			case -EINVAL:
+				memset(&key->ip, 0, sizeof(key->ip));
+				memset(&key->ipv6.addr, 0, sizeof(key->ipv6.addr));
+				/* fall-through */
+			case -EPROTO:
 				skb->transport_header = skb->network_header;
 				error = 0;
-			} else {
+				break;
+			default:
 				error = nh_len;
 			}
 			return error;
-- 
2.1.4

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