Merge branch 'skbuff-micro-optimize-flow-dissection'

Alexander Lobakin says:

====================
skbuff: micro-optimize flow dissection

This little number makes all of the flow dissection functions take
raw input data pointer as const (1-5) and shuffles the branches in
__skb_header_pointer() according to their hit probability.

The result is +20 Mbps per flow/core with one Flow Dissector pass
per packet. This affects RPS (with software hashing), drivers that
use eth_get_headlen() on their Rx path and so on.

From v2 [1]:
 - reword some commit messages as a potential fix for NIPA;
 - no functional changes.

From v1 [0]:
 - rebase on top of the latest net-next. This was super-weird, but
   I double-checked that the series applies with no conflicts, and
   then on Patchwork it didn't;
 - no other changes.

[0] https://lore.kernel.org/netdev/20210312194538.337504-1-alobakin@pm.me
[1] https://lore.kernel.org/netdev/20210313113645.5949-1-alobakin@pm.me
====================

Signed-off-by: David S. Miller <davem@davemloft.net>

2 files changed, 23 insertions, 20 deletions

diff --git a/net/core/flow_dissector.c b/net/core/flow_dissector.c
index 2ef2224b3bff..2ed380d096ce 100644
--- a/net/core/flow_dissector.c
+++ b/net/core/flow_dissector.c
@@ -114,7 +114,7 @@ int flow_dissector_bpf_prog_attach_check(struct net *net,
  * is the protocol port offset returned from proto_ports_offset
  */
 __be32 __skb_flow_get_ports(const struct sk_buff *skb, int thoff, u8 ip_proto,
-			    void *data, int hlen)
+			    const void *data, int hlen)
 {
 	int poff = proto_ports_offset(ip_proto);
 
@@ -161,7 +161,7 @@ static bool icmp_has_id(u8 type)
  */
 void skb_flow_get_icmp_tci(const struct sk_buff *skb,
 			   struct flow_dissector_key_icmp *key_icmp,
-			   void *data, int thoff, int hlen)
+			   const void *data, int thoff, int hlen)
 {
 	struct icmphdr *ih, _ih;
 
@@ -187,8 +187,8 @@ EXPORT_SYMBOL(skb_flow_get_icmp_tci);
  */
 static void __skb_flow_dissect_icmp(const struct sk_buff *skb,
 				    struct flow_dissector *flow_dissector,
-				    void *target_container,
-				    void *data, int thoff, int hlen)
+				    void *target_container, const void *data,
+				    int thoff, int hlen)
 {
 	struct flow_dissector_key_icmp *key_icmp;
 
@@ -409,8 +409,8 @@ EXPORT_SYMBOL(skb_flow_dissect_hash);
 static enum flow_dissect_ret
 __skb_flow_dissect_mpls(const struct sk_buff *skb,
 			struct flow_dissector *flow_dissector,
-			void *target_container, void *data, int nhoff, int hlen,
-			int lse_index, bool *entropy_label)
+			void *target_container, const void *data, int nhoff,
+			int hlen, int lse_index, bool *entropy_label)
 {
 	struct mpls_label *hdr, _hdr;
 	u32 entry, label, bos;
@@ -467,7 +467,8 @@ __skb_flow_dissect_mpls(const struct sk_buff *skb,
 static enum flow_dissect_ret
 __skb_flow_dissect_arp(const struct sk_buff *skb,
 		       struct flow_dissector *flow_dissector,
-		       void *target_container, void *data, int nhoff, int hlen)
+		       void *target_container, const void *data,
+		       int nhoff, int hlen)
 {
 	struct flow_dissector_key_arp *key_arp;
 	struct {
@@ -523,7 +524,7 @@ static enum flow_dissect_ret
 __skb_flow_dissect_gre(const struct sk_buff *skb,
 		       struct flow_dissector_key_control *key_control,
 		       struct flow_dissector *flow_dissector,
-		       void *target_container, void *data,
+		       void *target_container, const void *data,
 		       __be16 *p_proto, int *p_nhoff, int *p_hlen,
 		       unsigned int flags)
 {
@@ -663,8 +664,8 @@ __skb_flow_dissect_gre(const struct sk_buff *skb,
 static enum flow_dissect_ret
 __skb_flow_dissect_batadv(const struct sk_buff *skb,
 			  struct flow_dissector_key_control *key_control,
-			  void *data, __be16 *p_proto, int *p_nhoff, int hlen,
-			  unsigned int flags)
+			  const void *data, __be16 *p_proto, int *p_nhoff,
+			  int hlen, unsigned int flags)
 {
 	struct {
 		struct batadv_unicast_packet batadv_unicast;
@@ -695,7 +696,8 @@ __skb_flow_dissect_batadv(const struct sk_buff *skb,
 static void
 __skb_flow_dissect_tcp(const struct sk_buff *skb,
 		       struct flow_dissector *flow_dissector,
-		       void *target_container, void *data, int thoff, int hlen)
+		       void *target_container, const void *data,
+		       int thoff, int hlen)
 {
 	struct flow_dissector_key_tcp *key_tcp;
 	struct tcphdr *th, _th;
@@ -719,8 +721,8 @@ __skb_flow_dissect_tcp(const struct sk_buff *skb,
 static void
 __skb_flow_dissect_ports(const struct sk_buff *skb,
 			 struct flow_dissector *flow_dissector,
-			 void *target_container, void *data, int nhoff,
-			 u8 ip_proto, int hlen)
+			 void *target_container, const void *data,
+			 int nhoff, u8 ip_proto, int hlen)
 {
 	enum flow_dissector_key_id dissector_ports = FLOW_DISSECTOR_KEY_MAX;
 	struct flow_dissector_key_ports *key_ports;
@@ -744,7 +746,8 @@ __skb_flow_dissect_ports(const struct sk_buff *skb,
 static void
 __skb_flow_dissect_ipv4(const struct sk_buff *skb,
 			struct flow_dissector *flow_dissector,
-			void *target_container, void *data, const struct iphdr *iph)
+			void *target_container, const void *data,
+			const struct iphdr *iph)
 {
 	struct flow_dissector_key_ip *key_ip;
 
@@ -761,7 +764,8 @@ __skb_flow_dissect_ipv4(const struct sk_buff *skb,
 static void
 __skb_flow_dissect_ipv6(const struct sk_buff *skb,
 			struct flow_dissector *flow_dissector,
-			void *target_container, void *data, const struct ipv6hdr *iph)
+			void *target_container, const void *data,
+			const struct ipv6hdr *iph)
 {
 	struct flow_dissector_key_ip *key_ip;
 
@@ -908,9 +912,8 @@ bool bpf_flow_dissect(struct bpf_prog *prog, struct bpf_flow_dissector *ctx,
 bool __skb_flow_dissect(const struct net *net,
 			const struct sk_buff *skb,
 			struct flow_dissector *flow_dissector,
-			void *target_container,
-			void *data, __be16 proto, int nhoff, int hlen,
-			unsigned int flags)
+			void *target_container, const void *data,
+			__be16 proto, int nhoff, int hlen, unsigned int flags)
 {
 	struct flow_dissector_key_control *key_control;
 	struct flow_dissector_key_basic *key_basic;
@@ -1642,7 +1645,7 @@ __u32 skb_get_hash_perturb(const struct sk_buff *skb,
 }
 EXPORT_SYMBOL(skb_get_hash_perturb);
 
-u32 __skb_get_poff(const struct sk_buff *skb, void *data,
+u32 __skb_get_poff(const struct sk_buff *skb, const void *data,
 		   const struct flow_keys_basic *keys, int hlen)
 {
 	u32 poff = keys->control.thoff;
diff --git a/net/ethernet/eth.c b/net/ethernet/eth.c
index 4106373180c6..e01cf766d2c5 100644
--- a/net/ethernet/eth.c
+++ b/net/ethernet/eth.c
@@ -122,7 +122,7 @@ EXPORT_SYMBOL(eth_header);
  * Make a best effort attempt to pull the length for all of the headers for
  * a given frame in a linear buffer.
  */
-u32 eth_get_headlen(const struct net_device *dev, void *data, unsigned int len)
+u32 eth_get_headlen(const struct net_device *dev, const void *data, u32 len)
 {
 	const unsigned int flags = FLOW_DISSECTOR_F_PARSE_1ST_FRAG;
 	const struct ethhdr *eth = (const struct ethhdr *)data;