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net: Clarify meaning of CHECKSUM_PARTIAL for receive path

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The current meaning of CHECKSUM_PARTIAL for validating checksums
is that _all_ checksums in the packet are considered valid.
However, in the manner that CHECKSUM_PARTIAL is set only the checksum
at csum_start+csum_offset and any preceding checksums may
be considered valid. If there are checksums in the packet after
csum_offset it is possible they have not been verfied.

This patch changes CHECKSUM_PARTIAL logic in skb_csum_unnecessary and
__skb_gro_checksum_validate_needed to only considered checksums
referring to csum_start and any preceding checksums (with starting
offset before csum_start) to be verified.

Signed-off-by: Tom Herbert <therbert@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Tom Herbert 2015-02-10 16:30:28 -08:00 committed by David S. Miller
parent 26c4f7da3e
commit 6edec0e61b
2 changed files with 15 additions and 6 deletions
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4
include/linux/netdevice.h
View file

@ -2246,7 +2246,9 @@ static inline bool __skb_gro_checksum_validate_needed(struct sk_buff *skb,
bool zero_okay,
__sum16 check)
{
return (skb->ip_summed != CHECKSUM_PARTIAL &&
return ((skb->ip_summed != CHECKSUM_PARTIAL ||
skb_checksum_start_offset(skb) <
skb_gro_offset(skb)) &&
NAPI_GRO_CB(skb)->csum_cnt == 0 &&
(!zero_okay || check));
}

17
include/linux/skbuff.h
View file

@ -83,11 +83,15 @@
*
* CHECKSUM_PARTIAL:
*
* This is identical to the case for output below. This may occur on a packet
* A checksum is set up to be offloaded to a device as described in the
* output description for CHECKSUM_PARTIAL. This may occur on a packet
* received directly from another Linux OS, e.g., a virtualized Linux kernel
* on the same host. The packet can be treated in the same way as
* CHECKSUM_UNNECESSARY, except that on output (i.e., forwarding) the
* checksum must be filled in by the OS or the hardware.
* on the same host, or it may be set in the input path in GRO or remote
* checksum offload. For the purposes of checksum verification, the checksum
* referred to by skb->csum_start + skb->csum_offset and any preceding
* checksums in the packet are considered verified. Any checksums in the
* packet that are after the checksum being offloaded are not considered to
* be verified.
*
* B. Checksumming on output.
*
@ -2915,7 +2919,10 @@ __sum16 __skb_checksum_complete(struct sk_buff *skb);
static inline int skb_csum_unnecessary(const struct sk_buff *skb)
{
return ((skb->ip_summed & CHECKSUM_UNNECESSARY) || skb->csum_valid);
return ((skb->ip_summed == CHECKSUM_UNNECESSARY) ||
skb->csum_valid ||
(skb->ip_summed == CHECKSUM_PARTIAL &&
skb_checksum_start_offset(skb) >= 0));
}
/**