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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 <therbert@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>
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@ -567,7 +567,8 @@ struct sk_buff {
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* headers if needed
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*/
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__u8 encapsulation:1;
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/* 6/8 bit hole (depending on ndisc_nodetype presence) */
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__u8 encap_hdr_csum:1;
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/* 5/7 bit hole (depending on ndisc_nodetype presence) */
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kmemcheck_bitfield_end(flags2);
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#if defined CONFIG_NET_DMA || defined CONFIG_NET_RX_BUSY_POLL
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@ -2988,6 +2989,7 @@ static inline struct sec_path *skb_sec_path(struct sk_buff *skb)
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struct skb_gso_cb {
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int mac_offset;
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int encap_level;
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__u16 csum_start;
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};
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#define SKB_GSO_CB(skb) ((struct skb_gso_cb *)(skb)->cb)
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@ -3012,6 +3014,28 @@ static inline int gso_pskb_expand_head(struct sk_buff *skb, int extra)
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return 0;
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}
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/* Compute the checksum for a gso segment. First compute the checksum value
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* from the start of transport header to SKB_GSO_CB(skb)->csum_start, and
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* then add in skb->csum (checksum from csum_start to end of packet).
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* skb->csum and csum_start are then updated to reflect the checksum of the
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* resultant packet starting from the transport header-- the resultant checksum
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* is in the res argument (i.e. normally zero or ~ of checksum of a pseudo
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* header.
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*/
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static inline __sum16 gso_make_checksum(struct sk_buff *skb, __wsum res)
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{
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int plen = SKB_GSO_CB(skb)->csum_start - skb_headroom(skb) -
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skb_transport_offset(skb);
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__u16 csum;
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csum = csum_fold(csum_partial(skb_transport_header(skb),
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plen, skb->csum));
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skb->csum = res;
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SKB_GSO_CB(skb)->csum_start -= plen;
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return csum;
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}
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static inline bool skb_is_gso(const struct sk_buff *skb)
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{
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return skb_shinfo(skb)->gso_size;
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@ -2885,7 +2885,9 @@ struct sk_buff *skb_segment(struct sk_buff *head_skb,
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if (unlikely(!proto))
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return ERR_PTR(-EINVAL);
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csum = !!can_checksum_protocol(features, proto);
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csum = !head_skb->encap_hdr_csum &&
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!!can_checksum_protocol(features, proto);
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__skb_push(head_skb, doffset);
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headroom = skb_headroom(head_skb);
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pos = skb_headlen(head_skb);
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@ -2983,6 +2985,8 @@ struct sk_buff *skb_segment(struct sk_buff *head_skb,
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nskb->csum = skb_copy_and_csum_bits(head_skb, offset,
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skb_put(nskb, len),
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len, 0);
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SKB_GSO_CB(nskb)->csum_start =
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skb_headroom(nskb) + offset;
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continue;
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}
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@ -3052,6 +3056,8 @@ perform_csum_check:
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nskb->csum = skb_checksum(nskb, doffset,
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nskb->len - doffset, 0);
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nskb->ip_summed = CHECKSUM_NONE;
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SKB_GSO_CB(nskb)->csum_start =
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skb_headroom(nskb) + doffset;
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}
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} while ((offset += len) < head_skb->len);
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@ -135,6 +135,14 @@ struct sk_buff *iptunnel_handle_offloads(struct sk_buff *skb,
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return skb;
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}
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/* If packet is not gso and we are resolving any partial checksum,
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* clear encapsulation flag. This allows setting CHECKSUM_PARTIAL
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* on the outer header without confusing devices that implement
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* NETIF_F_IP_CSUM with encapsulation.
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*/
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if (csum_help)
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skb->encapsulation = 0;
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if (skb->ip_summed == CHECKSUM_PARTIAL && csum_help) {
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err = skb_checksum_help(skb);
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if (unlikely(err))
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