Commit a947b0a9 authored by Nicolas Dichtel's avatar Nicolas Dichtel Committed by Steffen Klassert
Browse files

xfrm: allow to avoid copying DSCP during encapsulation 



By default, DSCP is copying during encapsulation.
Copying the DSCP in IPsec tunneling may be a bit dangerous because packets with
different DSCP may get reordered relative to each other in the network and then
dropped by the remote IPsec GW if the reordering becomes too big compared to the
replay window.

It is possible to avoid this copy with netfilter rules, but it's very convenient
to be able to configure it for each SA directly.

This patch adds a toogle for this purpose. By default, it's not set to maintain
backward compatibility.

Field flags in struct xfrm_usersa_info is full, hence I add a new attribute.

Signed-off-by: default avatarNicolas Dichtel <nicolas.dichtel@6wind.com>
Signed-off-by: default avatarSteffen Klassert <steffen.klassert@secunet.com>
parent 6fac4115

include/net/xfrm.h

+1 −0
Original line number Diff line number Diff line
@@ -162,6 +162,7 @@ struct xfrm_state { 
		xfrm_address_t	saddr;

		int		header_len;

		int		trailer_len;

		u32		extra_flags;

	} props;



	struct xfrm_lifetime_cfg lft;

include/uapi/linux/xfrm.h

+3 −0
Original line number Diff line number Diff line
@@ -297,6 +297,7 @@ enum xfrm_attr_type_t { 
	XFRMA_MARK,		/* struct xfrm_mark */

	XFRMA_TFCPAD,		/* __u32 */

	XFRMA_REPLAY_ESN_VAL,	/* struct xfrm_replay_esn */

	XFRMA_SA_EXTRA_FLAGS,	/* __u32 */

	__XFRMA_MAX



#define XFRMA_MAX (__XFRMA_MAX - 1)
@@ -367,6 +368,8 @@ struct xfrm_usersa_info { 
#define XFRM_STATE_ESN		128

};



#define XFRM_SA_XFLAG_DONT_ENCAP_DSCP	1



struct xfrm_usersa_id {

	xfrm_address_t			daddr;

	__be32				spi;

net/ipv4/ipcomp.c

+1 −0
Original line number Diff line number Diff line
@@ -75,6 +75,7 @@ static struct xfrm_state *ipcomp_tunnel_create(struct xfrm_state *x) 
	t->props.mode = x->props.mode;

	t->props.saddr.a4 = x->props.saddr.a4;

	t->props.flags = x->props.flags;

	t->props.extra_flags = x->props.extra_flags;

	memcpy(&t->mark, &x->mark, sizeof(t->mark));



	if (xfrm_init_state(t))

net/ipv4/xfrm4_mode_tunnel.c

+6 −2
Original line number Diff line number Diff line
@@ -103,8 +103,12 @@ static int xfrm4_mode_tunnel_output(struct xfrm_state *x, struct sk_buff *skb) 


	top_iph->protocol = xfrm_af2proto(skb_dst(skb)->ops->family);



	/* DS disclosed */

	top_iph->tos = INET_ECN_encapsulate(XFRM_MODE_SKB_CB(skb)->tos,

	/* DS disclosing depends on XFRM_SA_XFLAG_DONT_ENCAP_DSCP */

	if (x->props.extra_flags & XFRM_SA_XFLAG_DONT_ENCAP_DSCP)

		top_iph->tos = 0;

	else

		top_iph->tos = XFRM_MODE_SKB_CB(skb)->tos;

	top_iph->tos = INET_ECN_encapsulate(top_iph->tos,

					    XFRM_MODE_SKB_CB(skb)->tos);



	flags = x->props.flags;

net/ipv6/xfrm6_mode_tunnel.c

+5 −2
Original line number Diff line number Diff line
@@ -49,8 +49,11 @@ static int xfrm6_mode_tunnel_output(struct xfrm_state *x, struct sk_buff *skb) 
	       sizeof(top_iph->flow_lbl));

	top_iph->nexthdr = xfrm_af2proto(skb_dst(skb)->ops->family);



	if (x->props.extra_flags & XFRM_SA_XFLAG_DONT_ENCAP_DSCP)

		dsfield = 0;

	else

		dsfield = XFRM_MODE_SKB_CB(skb)->tos;

	dsfield = INET_ECN_encapsulate(dsfield, dsfield);

	dsfield = INET_ECN_encapsulate(dsfield, XFRM_MODE_SKB_CB(skb)->tos);

	if (x->props.flags & XFRM_STATE_NOECN)

		dsfield &= ~INET_ECN_MASK;

	ipv6_change_dsfield(top_iph, 0, dsfield);

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