[PATCH net-next 1/2] net: Header length compution function
From: Amir Vadai <hidden>
Date: 2014-07-28 10:14:35
Subsystem:
networking [general], the rest · Maintainers:
"David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, Linus Torvalds
From: Eric Dumazet <redacted> This commit is based on Eric Dumazet suggestion. Use flow dissector to calculate header length. Tested the following with a mlx4, and it indeed speeds up GRE traffic, as GRO packets can now contain 17 MSS instead of 8. (Pulling payload means GRO had to use 2 'frags' per MSS) Signed-off-by: Eric Dumazet <redacted> Signed-off-by: Amir Vadai <redacted> --- include/linux/skbuff.h | 1 + net/core/flow_dissector.c | 24 ++++++++++++++++++++++++ 2 files changed, 25 insertions(+)
diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index b613557..1f9af4d 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h@@ -3133,6 +3133,7 @@ bool skb_partial_csum_set(struct sk_buff *skb, u16 start, u16 off); int skb_checksum_setup(struct sk_buff *skb, bool recalculate); u32 __skb_get_poff(const struct sk_buff *skb); +u32 eth_frame_headlen(void *data, unsigned int len); /** * skb_head_is_locked - Determine if the skb->head is locked down
diff --git a/net/core/flow_dissector.c b/net/core/flow_dissector.c
index 5f362c1..c3afd27 100644
--- a/net/core/flow_dissector.c
+++ b/net/core/flow_dissector.c@@ -343,6 +343,30 @@ u32 __skb_get_poff(const struct sk_buff *skb) return poff; } + +/* Helper to find length of headers in an ethernet frame. + * This can help drivers to pull exact amount of bytes into + * skb->head to get optimal GRO performance. + * TODO: Could also return rxhash while we do a complete flow dissection. + */ +u32 eth_frame_headlen(void *data, unsigned int len) +{ + const struct ethhdr *eth = data; + struct sk_buff skb; + + if (unlikely(len < ETH_HLEN)) + return len; + + skb.protocol = eth->h_proto; + skb.head = data + ETH_HLEN; + skb.data = skb.head; + skb_reset_network_header(&skb); + skb.len = len - ETH_HLEN; + skb.data_len = 0; + return __skb_get_poff(&skb) + ETH_HLEN; +} +EXPORT_SYMBOL(eth_frame_headlen); + static inline int get_xps_queue(struct net_device *dev, struct sk_buff *skb) { #ifdef CONFIG_XPS
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1.8.3.4