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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>
This commit is contained in:
Tom Herbert 2015-09-01 09:24:31 -07:00 committed by David S. Miller
parent 8306b688f1
commit 872b1abb1e
2 changed files with 5 additions and 1 deletions
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1
include/net/flow_dissector.h
View File

@ -126,6 +126,7 @@ enum flow_dissector_key_id {
#define FLOW_DISSECTOR_F_PARSE_1ST_FRAG BIT(0) #define FLOW_DISSECTOR_F_PARSE_1ST_FRAG BIT(0)
#define FLOW_DISSECTOR_F_STOP_AT_L3 BIT(1) #define FLOW_DISSECTOR_F_STOP_AT_L3 BIT(1)
#define FLOW_DISSECTOR_F_STOP_AT_FLOW_LABEL BIT(2)
struct flow_dissector_key { struct flow_dissector_key {
enum flow_dissector_key_id key_id; enum flow_dissector_key_id key_id;

5
net/core/flow_dissector.c
View File

@ -239,6 +239,8 @@ ipv6:
target_container); target_container);
key_tags->flow_label = ntohl(flow_label); 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) 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, static inline u32 ___skb_get_hash(const struct sk_buff *skb,
struct flow_keys *keys, u32 keyval) 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 0;
return __flow_hash_from_keys(keys, keyval); return __flow_hash_from_keys(keys, keyval);