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Commit a0ca153f authored by Alexander Duyck's avatar Alexander Duyck Committed by David S. Miller
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GRE: Disable segmentation offloads w/ CSUM and we are encapsulated via FOU 



This patch fixes an issue I found in which we were dropping frames if we
had enabled checksums on GRE headers that were encapsulated by either FOU
or GUE.  Without this patch I was barely able to get 1 Gb/s of throughput.
With this patch applied I am now at least getting around 6 Gb/s.

The issue is due to the fact that with FOU or GUE applied we do not provide
a transport offset pointing to the GRE header, nor do we offload it in
software as the GRE header is completely skipped by GSO and treated like a
VXLAN or GENEVE type header.  As such we need to prevent the stack from
generating it and also prevent GRE from generating it via any interface we
create.

Fixes: c3483384 ("gro: Allow tunnel stacking in the case of FOU/GUE")
Signed-off-by: default avatarAlexander Duyck <aduyck@mirantis.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 0a1a37b6

include/linux/netdevice.h

+4 −1
Original line number Diff line number Diff line
@@ -2120,7 +2120,10 @@ struct napi_gro_cb { 
	/* Used in foo-over-udp, set in udp[46]_gro_receive */

	u8	is_ipv6:1;



	/* 7 bit hole */

	/* Used in GRE, set in fou/gue_gro_receive */

	u8	is_fou:1;



	/* 6 bit hole */



	/* used to support CHECKSUM_COMPLETE for tunneling protocols */

	__wsum	csum;

net/core/dev.c

+1 −0
Original line number Diff line number Diff line
@@ -4439,6 +4439,7 @@ static enum gro_result dev_gro_receive(struct napi_struct *napi, struct sk_buff 
		NAPI_GRO_CB(skb)->flush = 0;

		NAPI_GRO_CB(skb)->free = 0;

		NAPI_GRO_CB(skb)->encap_mark = 0;

		NAPI_GRO_CB(skb)->is_fou = 0;

		NAPI_GRO_CB(skb)->gro_remcsum_start = 0;



		/* Setup for GRO checksum validation */

net/ipv4/fou.c

+6 −0
Original line number Diff line number Diff line
@@ -203,6 +203,9 @@ static struct sk_buff **fou_gro_receive(struct sk_buff **head, 
	 */

	NAPI_GRO_CB(skb)->encap_mark = 0;



	/* Flag this frame as already having an outer encap header */

	NAPI_GRO_CB(skb)->is_fou = 1;



	rcu_read_lock();

	offloads = NAPI_GRO_CB(skb)->is_ipv6 ? inet6_offloads : inet_offloads;

	ops = rcu_dereference(offloads[proto]);
@@ -368,6 +371,9 @@ static struct sk_buff **gue_gro_receive(struct sk_buff **head, 
	 */

	NAPI_GRO_CB(skb)->encap_mark = 0;



	/* Flag this frame as already having an outer encap header */

	NAPI_GRO_CB(skb)->is_fou = 1;



	rcu_read_lock();

	offloads = NAPI_GRO_CB(skb)->is_ipv6 ? inet6_offloads : inet_offloads;

	ops = rcu_dereference(offloads[guehdr->proto_ctype]);

net/ipv4/gre_offload.c

+8 −0
Original line number Diff line number Diff line
@@ -150,6 +150,14 @@ static struct sk_buff **gre_gro_receive(struct sk_buff **head, 
	if ((greh->flags & ~(GRE_KEY|GRE_CSUM)) != 0)

		goto out;



	/* We can only support GRE_CSUM if we can track the location of

	 * the GRE header.  In the case of FOU/GUE we cannot because the

	 * outer UDP header displaces the GRE header leaving us in a state

	 * of limbo.

	 */

	if ((greh->flags & GRE_CSUM) && NAPI_GRO_CB(skb)->is_fou)

		goto out;



	type = greh->protocol;



	rcu_read_lock();

net/ipv4/ip_gre.c

+10 −3
Original line number Diff line number Diff line
@@ -862,9 +862,16 @@ static void __gre_tunnel_init(struct net_device *dev) 
	dev->hw_features	|= GRE_FEATURES;



	if (!(tunnel->parms.o_flags & TUNNEL_SEQ)) {

		/* TCP offload with GRE SEQ is not supported. */

		/* TCP offload with GRE SEQ is not supported, nor

		 * can we support 2 levels of outer headers requiring

		 * an update.

		 */

		if (!(tunnel->parms.o_flags & TUNNEL_CSUM) ||

		    (tunnel->encap.type == TUNNEL_ENCAP_NONE)) {

			dev->features    |= NETIF_F_GSO_SOFTWARE;

			dev->hw_features |= NETIF_F_GSO_SOFTWARE;

		}



		/* Can use a lockless transmit, unless we generate

		 * output sequences

		 */