From 43948793f6d3a2c029b5bd3399d70904b910d668 Mon Sep 17 00:00:00 2001
From: Martynas Pumputis <martynasp@gmail.com>
Date: Mon, 30 Jan 2017 11:36:23 +0000
Subject: [PATCH] Add support of ESN

---
 nl/xfrm_state_linux.go | 55 +++++++++++++++++++++++++++++++++++-------
 xfrm_state.go          |  5 ++--
 xfrm_state_linux.go    | 29 ++++++++++++++++++++++
 3 files changed, 78 insertions(+), 11 deletions(-)

diff --git a/nl/xfrm_state_linux.go b/nl/xfrm_state_linux.go
index e5b9a09..b6290fd 100644
--- a/nl/xfrm_state_linux.go
+++ b/nl/xfrm_state_linux.go
@@ -5,15 +5,27 @@ import (
 )
 
 const (
-	SizeofXfrmUsersaId    = 0x18
-	SizeofXfrmStats       = 0x0c
-	SizeofXfrmUsersaInfo  = 0xe0
-	SizeofXfrmUserSpiInfo = 0xe8
-	SizeofXfrmAlgo        = 0x44
-	SizeofXfrmAlgoAuth    = 0x48
-	SizeofXfrmAlgoAEAD    = 0x48
-	SizeofXfrmEncapTmpl   = 0x18
-	SizeofXfrmUsersaFlush = 0x8
+	SizeofXfrmUsersaId       = 0x18
+	SizeofXfrmStats          = 0x0c
+	SizeofXfrmUsersaInfo     = 0xe0
+	SizeofXfrmUserSpiInfo    = 0xe8
+	SizeofXfrmAlgo           = 0x44
+	SizeofXfrmAlgoAuth       = 0x48
+	SizeofXfrmAlgoAEAD       = 0x48
+	SizeofXfrmEncapTmpl      = 0x18
+	SizeofXfrmUsersaFlush    = 0x8
+	SizeofXfrmReplayStateEsn = 0x18
+)
+
+const (
+	XFRM_STATE_NOECN      = 1
+	XFRM_STATE_DECAP_DSCP = 2
+	XFRM_STATE_NOPMTUDISC = 4
+	XFRM_STATE_WILDRECV   = 8
+	XFRM_STATE_ICMP       = 16
+	XFRM_STATE_AF_UNSPEC  = 32
+	XFRM_STATE_ALIGN4     = 64
+	XFRM_STATE_ESN        = 128
 )
 
 // struct xfrm_usersa_id {
@@ -295,3 +307,28 @@ func DeserializeXfrmUsersaFlush(b []byte) *XfrmUsersaFlush {
 func (msg *XfrmUsersaFlush) Serialize() []byte {
 	return (*(*[SizeofXfrmUsersaFlush]byte)(unsafe.Pointer(msg)))[:]
 }
+
+// struct xfrm_replay_state_esn {
+//     unsigned int    bmp_len;
+//     __u32           oseq;
+//     __u32           seq;
+//     __u32           oseq_hi;
+//     __u32           seq_hi;
+//     __u32           replay_window;
+//     __u32           bmp[0];
+// };
+
+type XfrmReplayStateEsn struct {
+	BmpLen       uint32
+	OSeq         uint32
+	Seq          uint32
+	OSeqHi       uint32
+	SeqHi        uint32
+	ReplayWindow uint32
+	Bmp          []uint32
+}
+
+func (msg *XfrmReplayStateEsn) Serialize() []byte {
+	// We deliberately do not pass Bmp, as it gets set by the kernel.
+	return (*(*[SizeofXfrmReplayStateEsn]byte)(unsafe.Pointer(msg)))[:]
+}
diff --git a/xfrm_state.go b/xfrm_state.go
index e25cde2..368a9b9 100644
--- a/xfrm_state.go
+++ b/xfrm_state.go
@@ -83,11 +83,12 @@ type XfrmState struct {
 	Crypt        *XfrmStateAlgo
 	Aead         *XfrmStateAlgo
 	Encap        *XfrmStateEncap
+	ESN          bool
 }
 
 func (sa XfrmState) String() string {
-	return fmt.Sprintf("Dst: %v, Src: %v, Proto: %s, Mode: %s, SPI: 0x%x, ReqID: 0x%x, ReplayWindow: %d, Mark: %v, Auth: %v, Crypt: %v, Aead: %v,Encap: %v",
-		sa.Dst, sa.Src, sa.Proto, sa.Mode, sa.Spi, sa.Reqid, sa.ReplayWindow, sa.Mark, sa.Auth, sa.Crypt, sa.Aead, sa.Encap)
+	return fmt.Sprintf("Dst: %v, Src: %v, Proto: %s, Mode: %s, SPI: 0x%x, ReqID: 0x%x, ReplayWindow: %d, Mark: %v, Auth: %v, Crypt: %v, Aead: %v, Encap: %v, ESN: %t",
+		sa.Dst, sa.Src, sa.Proto, sa.Mode, sa.Spi, sa.Reqid, sa.ReplayWindow, sa.Mark, sa.Auth, sa.Crypt, sa.Aead, sa.Encap, sa.ESN)
 }
 func (sa XfrmState) Print(stats bool) string {
 	if !stats {
diff --git a/xfrm_state_linux.go b/xfrm_state_linux.go
index dda4970..6a7bc0d 100644
--- a/xfrm_state_linux.go
+++ b/xfrm_state_linux.go
@@ -60,6 +60,21 @@ func writeMark(m *XfrmMark) []byte {
 	return mark.Serialize()
 }
 
+func writeReplayEsn(replayWindow int) []byte {
+	replayEsn := &nl.XfrmReplayStateEsn{
+		OSeq:         0,
+		Seq:          0,
+		OSeqHi:       0,
+		SeqHi:        0,
+		ReplayWindow: uint32(replayWindow),
+	}
+
+	// taken from iproute2/ip/xfrm_state.c:
+	replayEsn.BmpLen = uint32((replayWindow + (4 * 8) - 1) / (4 * 8))
+
+	return replayEsn.Serialize()
+}
+
 // XfrmStateAdd will add an xfrm state to the system.
 // Equivalent to: `ip xfrm state add $state`
 func XfrmStateAdd(state *XfrmState) error {
@@ -91,6 +106,7 @@ func (h *Handle) XfrmStateUpdate(state *XfrmState) error {
 }
 
 func (h *Handle) xfrmStateAddOrUpdate(state *XfrmState, nlProto int) error {
+
 	// A state with spi 0 can't be deleted so don't allow it to be set
 	if state.Spi == 0 {
 		return fmt.Errorf("Spi must be set when adding xfrm state.")
@@ -98,6 +114,15 @@ func (h *Handle) xfrmStateAddOrUpdate(state *XfrmState, nlProto int) error {
 	req := h.newNetlinkRequest(nlProto, syscall.NLM_F_CREATE|syscall.NLM_F_EXCL|syscall.NLM_F_ACK)
 
 	msg := xfrmUsersaInfoFromXfrmState(state)
+
+	if state.ESN {
+		if state.ReplayWindow == 0 {
+			return fmt.Errorf("ESN flag set without ReplayWindow")
+		}
+		msg.Flags |= nl.XFRM_STATE_ESN
+		msg.ReplayWindow = 0
+	}
+
 	limitsToLft(state.Limits, &msg.Lft)
 	req.AddData(msg)
 
@@ -127,6 +152,10 @@ func (h *Handle) xfrmStateAddOrUpdate(state *XfrmState, nlProto int) error {
 		out := nl.NewRtAttr(nl.XFRMA_MARK, writeMark(state.Mark))
 		req.AddData(out)
 	}
+	if state.ESN {
+		out := nl.NewRtAttr(nl.XFRMA_REPLAY_ESN_VAL, writeReplayEsn(state.ReplayWindow))
+		req.AddData(out)
+	}
 
 	_, err := req.Execute(syscall.NETLINK_XFRM, 0)
 	return err