From 7e2b10c1e52ca37fb522be49f4be367f9311d0cd Mon Sep 17 00:00:00 2001 From: Tom Herbert Date: Wed, 4 Jun 2014 17:20:02 -0700 Subject: [PATCH] net: Support for multiple checksums with gso When creating a GSO packet segment we may need to set more than one checksum in the packet (for instance a TCP checksum and UDP checksum for VXLAN encapsulation). To be efficient, we want to do checksum calculation for any part of the packet at most once. This patch adds csum_start offset to skb_gso_cb. This tracks the starting offset for skb->csum which is initially set in skb_segment. When a protocol needs to compute a transport checksum it calls gso_make_checksum which computes the checksum value from the start of transport header to csum_start and then adds in skb->csum to get the full checksum. skb->csum and csum_start are then updated to reflect the checksum of the resultant packet starting from the transport header. This patch also adds a flag to skbuff, encap_hdr_csum, which is set in *gso_segment fucntions to indicate that a tunnel protocol needs checksum calculation Signed-off-by: Tom Herbert Signed-off-by: David S. Miller --- include/linux/skbuff.h | 26 +++++++++++++++++++++++++- net/core/skbuff.c | 8 +++++++- net/ipv4/ip_tunnel_core.c | 8 ++++++++ 3 files changed, 40 insertions(+), 2 deletions(-) diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h index 7a9beeb1c458..d8d397acb52c 100644 --- a/include/linux/skbuff.h +++ b/include/linux/skbuff.h @@ -567,7 +567,8 @@ struct sk_buff { * headers if needed */ __u8 encapsulation:1; - /* 6/8 bit hole (depending on ndisc_nodetype presence) */ + __u8 encap_hdr_csum:1; + /* 5/7 bit hole (depending on ndisc_nodetype presence) */ kmemcheck_bitfield_end(flags2); #if defined CONFIG_NET_DMA || defined CONFIG_NET_RX_BUSY_POLL @@ -2988,6 +2989,7 @@ static inline struct sec_path *skb_sec_path(struct sk_buff *skb) struct skb_gso_cb { int mac_offset; int encap_level; + __u16 csum_start; }; #define SKB_GSO_CB(skb) ((struct skb_gso_cb *)(skb)->cb) @@ -3012,6 +3014,28 @@ static inline int gso_pskb_expand_head(struct sk_buff *skb, int extra) return 0; } +/* Compute the checksum for a gso segment. First compute the checksum value + * from the start of transport header to SKB_GSO_CB(skb)->csum_start, and + * then add in skb->csum (checksum from csum_start to end of packet). + * skb->csum and csum_start are then updated to reflect the checksum of the + * resultant packet starting from the transport header-- the resultant checksum + * is in the res argument (i.e. normally zero or ~ of checksum of a pseudo + * header. + */ +static inline __sum16 gso_make_checksum(struct sk_buff *skb, __wsum res) +{ + int plen = SKB_GSO_CB(skb)->csum_start - skb_headroom(skb) - + skb_transport_offset(skb); + __u16 csum; + + csum = csum_fold(csum_partial(skb_transport_header(skb), + plen, skb->csum)); + skb->csum = res; + SKB_GSO_CB(skb)->csum_start -= plen; + + return csum; +} + static inline bool skb_is_gso(const struct sk_buff *skb) { return skb_shinfo(skb)->gso_size; diff --git a/net/core/skbuff.c b/net/core/skbuff.c index 3f6c7e8be8a4..05f4bef2ce12 100644 --- a/net/core/skbuff.c +++ b/net/core/skbuff.c @@ -2885,7 +2885,9 @@ struct sk_buff *skb_segment(struct sk_buff *head_skb, if (unlikely(!proto)) return ERR_PTR(-EINVAL); - csum = !!can_checksum_protocol(features, proto); + csum = !head_skb->encap_hdr_csum && + !!can_checksum_protocol(features, proto); + __skb_push(head_skb, doffset); headroom = skb_headroom(head_skb); pos = skb_headlen(head_skb); @@ -2983,6 +2985,8 @@ struct sk_buff *skb_segment(struct sk_buff *head_skb, nskb->csum = skb_copy_and_csum_bits(head_skb, offset, skb_put(nskb, len), len, 0); + SKB_GSO_CB(nskb)->csum_start = + skb_headroom(nskb) + offset; continue; } @@ -3052,6 +3056,8 @@ perform_csum_check: nskb->csum = skb_checksum(nskb, doffset, nskb->len - doffset, 0); nskb->ip_summed = CHECKSUM_NONE; + SKB_GSO_CB(nskb)->csum_start = + skb_headroom(nskb) + doffset; } } while ((offset += len) < head_skb->len); diff --git a/net/ipv4/ip_tunnel_core.c b/net/ipv4/ip_tunnel_core.c index 847e69cbff7e..f4c987bb7e94 100644 --- a/net/ipv4/ip_tunnel_core.c +++ b/net/ipv4/ip_tunnel_core.c @@ -135,6 +135,14 @@ struct sk_buff *iptunnel_handle_offloads(struct sk_buff *skb, return skb; } + /* If packet is not gso and we are resolving any partial checksum, + * clear encapsulation flag. This allows setting CHECKSUM_PARTIAL + * on the outer header without confusing devices that implement + * NETIF_F_IP_CSUM with encapsulation. + */ + if (csum_help) + skb->encapsulation = 0; + if (skb->ip_summed == CHECKSUM_PARTIAL && csum_help) { err = skb_checksum_help(skb); if (unlikely(err))