netdev - [PATCH net-next] xfrm: no-anti-replay protection flag

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Date:   Mon, 25 May 2020 17:46:33 +0200
From:   Petr Vaněk <pv@...ello.cz>
To:     Steffen Klassert <steffen.klassert@...unet.com>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Cc:     Petr Vaněk <pv@...ello.cz>
Subject: [PATCH net-next] xfrm: no-anti-replay protection flag

RFC 4303 in section 3.3.3 suggests to disable anti-replay for manually
distributed ICVs.

This patch introduces new extra_flag XFRM_SA_XFLAG_NO_ANTI_REPLAY which
disables anti-replay for outbound packets if set. The flag is used only
in legacy and bmp code, because esn should not be negotiated if
anti-replay is disabled (see note in 3.3.3 section).

Signed-off-by: Petr Vaněk <pv@...ello.cz>
---
 include/uapi/linux/xfrm.h |  1 +
 net/xfrm/xfrm_replay.c    | 12 ++++++++----
 2 files changed, 9 insertions(+), 4 deletions(-)

diff --git a/include/uapi/linux/xfrm.h b/include/uapi/linux/xfrm.h
index 5f3b9fec7b5f..4842b1ed49e9 100644
--- a/include/uapi/linux/xfrm.h
+++ b/include/uapi/linux/xfrm.h
@@ -387,6 +387,7 @@ struct xfrm_usersa_info {
 };
 
 #define XFRM_SA_XFLAG_DONT_ENCAP_DSCP	1
+#define XFRM_SA_XFLAG_NO_ANTI_REPLAY	2
 
 struct xfrm_usersa_id {
 	xfrm_address_t			daddr;
diff --git a/net/xfrm/xfrm_replay.c b/net/xfrm/xfrm_replay.c
index 98943f8d01aa..1602843aa2ec 100644
--- a/net/xfrm/xfrm_replay.c
+++ b/net/xfrm/xfrm_replay.c
@@ -89,7 +89,8 @@ static int xfrm_replay_overflow(struct xfrm_state *x, struct sk_buff *skb)
 	if (x->type->flags & XFRM_TYPE_REPLAY_PROT) {
 		XFRM_SKB_CB(skb)->seq.output.low = ++x->replay.oseq;
 		XFRM_SKB_CB(skb)->seq.output.hi = 0;
-		if (unlikely(x->replay.oseq == 0)) {
+		if (unlikely(x->replay.oseq == 0) &&
+		    !(x->props.extra_flags & XFRM_SA_XFLAG_NO_ANTI_REPLAY)) {
 			x->replay.oseq--;
 			xfrm_audit_state_replay_overflow(x, skb);
 			err = -EOVERFLOW;
@@ -168,7 +169,8 @@ static int xfrm_replay_overflow_bmp(struct xfrm_state *x, struct sk_buff *skb)
 	if (x->type->flags & XFRM_TYPE_REPLAY_PROT) {
 		XFRM_SKB_CB(skb)->seq.output.low = ++replay_esn->oseq;
 		XFRM_SKB_CB(skb)->seq.output.hi = 0;
-		if (unlikely(replay_esn->oseq == 0)) {
+		if (unlikely(replay_esn->oseq == 0) &&
+		    !(x->props.extra_flags & XFRM_SA_XFLAG_NO_ANTI_REPLAY)) {
 			replay_esn->oseq--;
 			xfrm_audit_state_replay_overflow(x, skb);
 			err = -EOVERFLOW;
@@ -572,7 +574,8 @@ static int xfrm_replay_overflow_offload(struct xfrm_state *x, struct sk_buff *sk
 
 		XFRM_SKB_CB(skb)->seq.output.hi = 0;
 		xo->seq.hi = 0;
-		if (unlikely(oseq < x->replay.oseq)) {
+		if (unlikely(oseq < x->replay.oseq) &&
+		    !(x->props.extra_flags & XFRM_SA_XFLAG_NO_ANTI_REPLAY)) {
 			xfrm_audit_state_replay_overflow(x, skb);
 			err = -EOVERFLOW;
 
@@ -611,7 +614,8 @@ static int xfrm_replay_overflow_offload_bmp(struct xfrm_state *x, struct sk_buff
 
 		XFRM_SKB_CB(skb)->seq.output.hi = 0;
 		xo->seq.hi = 0;
-		if (unlikely(oseq < replay_esn->oseq)) {
+		if (unlikely(oseq < replay_esn->oseq) &&
+		    !(x->props.extra_flags & XFRM_SA_XFLAG_NO_ANTI_REPLAY)) {
 			xfrm_audit_state_replay_overflow(x, skb);
 			err = -EOVERFLOW;
 
-- 
2.26.2