flow_dissector: Add flag to stop parsing when an IPv6 flow label is seen

Add an input flag to flow dissector on rather dissection should be
stopped when a flow label is encountered. Presumably, the flow label
is derived from a sufficient hash of an inner transport packet so
further dissection is not needed (that is ports are not included in
the flow hash). Using the flow label instead of ports has the additional
benefit that packet fragments should hash to same value as non-fragments
for a flow (assuming that the same flow label is used).

We set this flag by default in for skb_get_hash.

Signed-off-by: Tom Herbert <tom@herbertland.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/include/net/flow_dissector.h b/include/net/flow_dissector.h
index bb81e3b576e709272a40efd0948de44915f7bce3..66dbc3498efb2636b8c441793d9716b2f854fa0c 100644 (file)
--- a/include/net/flow_dissector.h
+++ b/include/net/flow_dissector.h
@@ -126,6 +126,7 @@ enum flow_dissector_key_id {
 
 #define FLOW_DISSECTOR_F_PARSE_1ST_FRAG                BIT(0)
 #define FLOW_DISSECTOR_F_STOP_AT_L3            BIT(1)
+#define FLOW_DISSECTOR_F_STOP_AT_FLOW_LABEL    BIT(2)
 
 struct flow_dissector_key {
        enum flow_dissector_key_id key_id;

diff --git a/net/core/flow_dissector.c b/net/core/flow_dissector.c
index 94fd841f341f16fd0d4476ee52f28bfde29909dc..094e34354627b6b001f17ce97d8d86435d945648 100644 (file)
--- a/net/core/flow_dissector.c
+++ b/net/core/flow_dissector.c
@@ -239,6 +239,8 @@ ipv6:
                                                                     target_container);
                                key_tags->flow_label = ntohl(flow_label);
                        }
+                       if (flags & FLOW_DISSECTOR_F_STOP_AT_FLOW_LABEL)
+                               goto out_good;
                }
 
                if (flags & FLOW_DISSECTOR_F_STOP_AT_L3)
@@ -599,7 +601,8 @@ EXPORT_SYMBOL(flow_hash_from_keys);
 static inline u32 ___skb_get_hash(const struct sk_buff *skb,
                                  struct flow_keys *keys, u32 keyval)
 {
-       if (!skb_flow_dissect_flow_keys(skb, keys, 0))
+       if (!skb_flow_dissect_flow_keys(skb, keys,
+                                       FLOW_DISSECTOR_F_STOP_AT_FLOW_LABEL))
                return 0;
 
        return __flow_hash_from_keys(keys, keyval);