Commit 72a338bc authored by Paolo Abeni's avatar Paolo Abeni Committed by David S. Miller
Browse files

net: core: rework basic flow dissection helper 



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: default avatarDavid Miller <davem@davemloft.net>
Signed-off-by: default avatarPaolo Abeni <pabeni@redhat.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 62515f95

include/linux/skbuff.h

+10 −8
Original line number Diff line number Diff line
@@ -1171,7 +1171,7 @@ void __skb_get_hash(struct sk_buff *skb); 
u32 __skb_get_hash_symmetric(const struct sk_buff *skb);

u32 skb_get_poff(const struct sk_buff *skb);

u32 __skb_get_poff(const struct sk_buff *skb, void *data,

		   const struct flow_keys *keys, int hlen);

		   const struct flow_keys_basic *keys, int hlen);

__be32 __skb_flow_get_ports(const struct sk_buff *skb, int thoff, u8 ip_proto,

			    void *data, int hlen_proto);
@@ -1208,13 +1208,14 @@ static inline bool skb_flow_dissect_flow_keys(const struct sk_buff *skb, 
				  NULL, 0, 0, 0, flags);

}



static inline bool skb_flow_dissect_flow_keys_buf(struct flow_keys *flow,

						  void *data, __be16 proto,

						  int nhoff, int hlen,

static inline bool

skb_flow_dissect_flow_keys_basic(const struct sk_buff *skb,

				 struct flow_keys_basic *flow, void *data,

				 __be16 proto, int nhoff, int hlen,

				 unsigned int flags)

{

	memset(flow, 0, sizeof(*flow));

	return __skb_flow_dissect(NULL, &flow_keys_buf_dissector, flow,

	return __skb_flow_dissect(skb, &flow_keys_basic_dissector, flow,

				  data, proto, nhoff, hlen, flags);

}
@@ -2350,11 +2351,12 @@ static inline void skb_pop_mac_header(struct sk_buff *skb) 
static inline void skb_probe_transport_header(struct sk_buff *skb,

					      const int offset_hint)

{

	struct flow_keys keys;

	struct flow_keys_basic keys;



	if (skb_transport_header_was_set(skb))

		return;

	else if (skb_flow_dissect_flow_keys(skb, &keys, 0))



	if (skb_flow_dissect_flow_keys_basic(skb, &keys, 0, 0, 0, 0, 0))

		skb_set_transport_header(skb, keys.control.thoff);

	else

		skb_set_transport_header(skb, offset_hint);

include/net/flow_dissector.h

+6 −1
Original line number Diff line number Diff line
@@ -226,6 +226,11 @@ struct flow_dissector { 
	unsigned short int offset[FLOW_DISSECTOR_KEY_MAX];

};



struct flow_keys_basic {

	struct flow_dissector_key_control control;

	struct flow_dissector_key_basic basic;

};



struct flow_keys {

	struct flow_dissector_key_control control;

#define FLOW_KEYS_HASH_START_FIELD basic
@@ -244,7 +249,7 @@ __be32 flow_get_u32_src(const struct flow_keys *flow); 
__be32 flow_get_u32_dst(const struct flow_keys *flow);



extern struct flow_dissector flow_keys_dissector;

extern struct flow_dissector flow_keys_buf_dissector;

extern struct flow_dissector flow_keys_basic_dissector;



/* struct flow_keys_digest:

 *

net/core/flow_dissector.c

+9 −8
Original line number Diff line number Diff line
@@ -1253,7 +1253,7 @@ __u32 skb_get_hash_perturb(const struct sk_buff *skb, u32 perturb) 
EXPORT_SYMBOL(skb_get_hash_perturb);



u32 __skb_get_poff(const struct sk_buff *skb, void *data,

		   const struct flow_keys *keys, int hlen)

		   const struct flow_keys_basic *keys, int hlen)

{

	u32 poff = keys->control.thoff;
@@ -1314,9 +1314,9 @@ u32 __skb_get_poff(const struct sk_buff *skb, void *data, 
 */

u32 skb_get_poff(const struct sk_buff *skb)

{

	struct flow_keys keys;

	struct flow_keys_basic keys;



	if (!skb_flow_dissect_flow_keys(skb, &keys, 0))

	if (!skb_flow_dissect_flow_keys_basic(skb, &keys, 0, 0, 0, 0, 0))

		return 0;



	return __skb_get_poff(skb, skb->data, &keys, skb_headlen(skb));
@@ -1403,7 +1403,7 @@ static const struct flow_dissector_key flow_keys_dissector_symmetric_keys[] = { 
	},

};



static const struct flow_dissector_key flow_keys_buf_dissector_keys[] = {

static const struct flow_dissector_key flow_keys_basic_dissector_keys[] = {

	{

		.key_id = FLOW_DISSECTOR_KEY_CONTROL,

		.offset = offsetof(struct flow_keys, control),
@@ -1417,7 +1417,8 @@ static const struct flow_dissector_key flow_keys_buf_dissector_keys[] = { 
struct flow_dissector flow_keys_dissector __read_mostly;

EXPORT_SYMBOL(flow_keys_dissector);



struct flow_dissector flow_keys_buf_dissector __read_mostly;

struct flow_dissector flow_keys_basic_dissector __read_mostly;

EXPORT_SYMBOL(flow_keys_basic_dissector);



static int __init init_default_flow_dissectors(void)

{
@@ -1427,9 +1428,9 @@ static int __init init_default_flow_dissectors(void) 
	skb_flow_dissector_init(&flow_keys_dissector_symmetric,

				flow_keys_dissector_symmetric_keys,

				ARRAY_SIZE(flow_keys_dissector_symmetric_keys));

	skb_flow_dissector_init(&flow_keys_buf_dissector,

				flow_keys_buf_dissector_keys,

				ARRAY_SIZE(flow_keys_buf_dissector_keys));

	skb_flow_dissector_init(&flow_keys_basic_dissector,

				flow_keys_basic_dissector_keys,

				ARRAY_SIZE(flow_keys_basic_dissector_keys));

	return 0;

}

net/ethernet/eth.c

+3 −3
Original line number Diff line number Diff line
@@ -128,14 +128,14 @@ 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,

	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));

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