Re: [PATCH net-next v8] net: openvswitch: IPv6: Add IPv6 extension header support

On Thu, Dec 2, 2021 at 12:20 PM Cpp Code [off-list ref] wrote:

On Wed, Dec 1, 2021 at 11:34 PM Pravin Shelar [off-list ref] wrote:

quoted

On Wed, Nov 24, 2021 at 11:33 AM Toms Atteka [off-list ref] wrote:

quoted

This change adds a new OpenFlow field OFPXMT_OFB_IPV6_EXTHDR and
packets can be filtered using ipv6_ext flag.

Signed-off-by: Toms Atteka <redacted>
---
 include/uapi/linux/openvswitch.h |   6 ++
 net/openvswitch/flow.c           | 140 +++++++++++++++++++++++++++++++
 net/openvswitch/flow.h           |  14 ++++
 net/openvswitch/flow_netlink.c   |  26 +++++-
 4 files changed, 184 insertions(+), 2 deletions(-)

diff --git a/include/uapi/linux/openvswitch.h b/include/uapi/linux/openvswitch.h
index a87b44cd5590..43790f07e4a2 100644
--- a/include/uapi/linux/openvswitch.h
+++ b/include/uapi/linux/openvswitch.h

@@ -342,6 +342,7 @@ enum ovs_key_attr {
        OVS_KEY_ATTR_CT_ORIG_TUPLE_IPV4,   /* struct ovs_key_ct_tuple_ipv4 */
        OVS_KEY_ATTR_CT_ORIG_TUPLE_IPV6,   /* struct ovs_key_ct_tuple_ipv6 */
        OVS_KEY_ATTR_NSH,       /* Nested set of ovs_nsh_key_* */
+       OVS_KEY_ATTR_IPV6_EXTHDRS,  /* struct ovs_key_ipv6_exthdr */

 #ifdef __KERNEL__
        OVS_KEY_ATTR_TUNNEL_INFO,  /* struct ip_tunnel_info */

@@ -421,6 +422,11 @@ struct ovs_key_ipv6 {
        __u8   ipv6_frag;       /* One of OVS_FRAG_TYPE_*. */
 };

+/* separate structure to support backward compatibility with older user space */
+struct ovs_key_ipv6_exthdrs {
+       __u16  hdrs;
+};
+
 struct ovs_key_tcp {
        __be16 tcp_src;
        __be16 tcp_dst;

diff --git a/net/openvswitch/flow.c b/net/openvswitch/flow.c
index 9d375e74b607..28acb40437ca 100644
--- a/net/openvswitch/flow.c
+++ b/net/openvswitch/flow.c

@@ -239,6 +239,144 @@ static bool icmphdr_ok(struct sk_buff *skb)
                                  sizeof(struct icmphdr));
 }

+/**
+ * get_ipv6_ext_hdrs() - Parses packet and sets IPv6 extension header flags.
+ *
+ * @skb: buffer where extension header data starts in packet
+ * @nh: ipv6 header
+ * @ext_hdrs: flags are stored here
+ *
+ * OFPIEH12_UNREP is set if more than one of a given IPv6 extension header
+ * is unexpectedly encountered. (Two destination options headers may be
+ * expected and would not cause this bit to be set.)
+ *
+ * OFPIEH12_UNSEQ is set if IPv6 extension headers were not in the order
+ * preferred (but not required) by RFC 2460:
+ *
+ * When more than one extension header is used in the same packet, it is
+ * recommended that those headers appear in the following order:
+ *      IPv6 header
+ *      Hop-by-Hop Options header
+ *      Destination Options header
+ *      Routing header
+ *      Fragment header
+ *      Authentication header
+ *      Encapsulating Security Payload header
+ *      Destination Options header
+ *      upper-layer header
+ */
+static void get_ipv6_ext_hdrs(struct sk_buff *skb, struct ipv6hdr *nh,
+                             u16 *ext_hdrs)
+{
+       u8 next_type = nh->nexthdr;
+       unsigned int start = skb_network_offset(skb) + sizeof(struct ipv6hdr);
+       int dest_options_header_count = 0;
+
+       *ext_hdrs = 0;
+
+       while (ipv6_ext_hdr(next_type)) {
+               struct ipv6_opt_hdr _hdr, *hp;
+
+               switch (next_type) {
+               case IPPROTO_NONE:
+                       *ext_hdrs |= OFPIEH12_NONEXT;
+                       /* stop parsing */
+                       return;
+
+               case IPPROTO_ESP:
+                       if (*ext_hdrs & OFPIEH12_ESP)
+                               *ext_hdrs |= OFPIEH12_UNREP;
+                       if ((*ext_hdrs & ~(OFPIEH12_HOP | OFPIEH12_DEST |
+                                          OFPIEH12_ROUTER | IPPROTO_FRAGMENT |
+                                          OFPIEH12_AUTH | OFPIEH12_UNREP)) ||
+                           dest_options_header_count >= 2) {
+                               *ext_hdrs |= OFPIEH12_UNSEQ;
+                       }
+                       *ext_hdrs |= OFPIEH12_ESP;
+                       break;

you need to check_header() before looking into each extension header.

Could you elaborate why I need to add check_header(),
skb_header_pointer() is doing sanitization.

I mean check_header() would allow you to read the header without
copying the bits, it is used in ovs flow extraction so its usual
check.