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net: core: rework basic flow dissection helper

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When the core networking needs to detect the transport offset in a given
packet and parse it explicitly, a full-blown flow_keys struct is used for
storage.
This patch introduces a smaller keys store, rework the basic flow dissect
helper to use it, and apply this new helper where possible - namely in
skb_probe_transport_header(). The used flow dissector data structures
are renamed to match more closely the new role.

The above gives ~50% performance improvement in micro benchmarking around
skb_probe_transport_header() and ~30% around eth_get_headlen(), mostly due
to the smaller memset. Small, but measurable improvement is measured also
in macro benchmarking.

v1 -> v2: use the new helper in eth_get_headlen() and skb_get_poff(),
  as per DaveM suggestion

Suggested-by: David Miller <davem@davemloft.net>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Paolo Abeni 2018-05-04 11:32:59 +02:00 • committed by David S. Miller
parent 62515f95b4
commit 72a338bcc6
4 changed files with 28 additions and 20 deletions
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6
net/ethernet/eth.c
View file

@ -128,15 +128,15 @@ u32 eth_get_headlen(void *data, unsigned int len)
{
const unsigned int flags = FLOW_DISSECTOR_F_PARSE_1ST_FRAG;
const struct ethhdr *eth = (const struct ethhdr *)data;
struct flow_keys keys;
struct flow_keys_basic keys;
/* this should never happen, but better safe than sorry */
if (unlikely(len < sizeof(*eth)))
return len;
/* parse any remaining L2/L3 headers, check for L4 */
if (!skb_flow_dissect_flow_keys_buf(&keys, data, eth->h_proto,
sizeof(*eth), len, flags))
if (!skb_flow_dissect_flow_keys_basic(NULL, &keys, data, eth->h_proto,
sizeof(*eth), len, flags))
return max_t(u32, keys.control.thoff, sizeof(*eth));
/* parse for any L4 headers */