Commit 6edec0e6 authored by Tom Herbert's avatar Tom Herbert Committed by David S. Miller
Browse files

net: Clarify meaning of CHECKSUM_PARTIAL for receive path 



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: default avatarTom Herbert <therbert@google.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 26c4f7da

include/linux/netdevice.h

+3 −1
Original line number Diff line number Diff line
@@ -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));

}

include/linux/skbuff.h

+12 −5
Original line number Diff line number Diff line
@@ -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));

}



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