Merge branch 'Support IPsec crypto offload for IPv6 ESP and IPv4 UDP-encapsulated ESP data paths'

Mike Yu says:

====================
Currently, IPsec crypto offload is enabled for GRO code path. However, there
are other code paths where the XFRM stack is involved; for example, IPv6 ESP
packets handled by xfrm6_esp_rcv() in ESP layer, and IPv4 UDP-encapsulated
ESP packets handled by udp_rcv() in UDP layer.

This patchset extends the crypto offload support to cover these two cases.
This is useful for devices with traffic accounting (e.g., Android), where GRO
can lead to inaccurate accounting on the underlying network. For example, VPN
traffic might not be counted on the wifi network interface wlan0 if the packets
are handled in GRO code path before entering the network stack for accounting.

Below is the RX data path scenario the crypto offload can be applied to.

  +-----------+   +-------+
  | HW Driver |-->| wlan0 |--------+
  +-----------+   +-------+        |
                                   v
                             +---------------+   +------+
                     +------>| Network Stack |-->| Apps |
                     |       +---------------+   +------+
                     |             |
                     |             v
                 +--------+   +------------+
                 | ipsec1 |<--| XFRM Stack |
                 +--------+   +------------+
====================
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>

net/ipv4/esp4.c

@@ -349,6 +349,7 @@ static struct ip_esp_hdr *esp_output_udp_encap(struct sk_buff *skb,
 {
 	struct udphdr *uh;
 	unsigned int len;
+	struct xfrm_offload *xo = xfrm_offload(skb);
 
 	len = skb->len + esp->tailen - skb_transport_offset(skb);
 	if (len + sizeof(struct iphdr) > IP_MAX_MTU)
@@ -360,7 +361,12 @@ static struct ip_esp_hdr *esp_output_udp_encap(struct sk_buff *skb,
 	uh->len = htons(len);
 	uh->check = 0;
 
-	*skb_mac_header(skb) = IPPROTO_UDP;
+	/* For IPv4 ESP with UDP encapsulation, if xo is not null, the skb is in the crypto offload
+	 * data path, which means that esp_output_udp_encap is called outside of the XFRM stack.
+	 * In this case, the mac header doesn't point to the IPv4 protocol field, so don't set it.
+	 */
+	if (!xo || encap_type != UDP_ENCAP_ESPINUDP)
+		*skb_mac_header(skb) = IPPROTO_UDP;
 
 	return (struct ip_esp_hdr *)(uh + 1);
 }

net/ipv4/esp4_offload.c

@@ -264,6 +264,7 @@ static int esp_xmit(struct xfrm_state *x, struct sk_buff *skb,  netdev_features_
 	struct esp_info esp;
 	bool hw_offload = true;
 	__u32 seq;
+	int encap_type = 0;
 
 	esp.inplace = true;
 
@@ -296,8 +297,10 @@ static int esp_xmit(struct xfrm_state *x, struct sk_buff *skb,  netdev_features_
 
 	esp.esph = ip_esp_hdr(skb);
 
+	if (x->encap)
+		encap_type = x->encap->encap_type;
 
-	if (!hw_offload || !skb_is_gso(skb)) {
+	if (!hw_offload || !skb_is_gso(skb) || (hw_offload && encap_type == UDP_ENCAP_ESPINUDP)) {
 		esp.nfrags = esp_output_head(x, skb, &esp);
 		if (esp.nfrags < 0)
 			return esp.nfrags;
@@ -324,6 +327,18 @@ static int esp_xmit(struct xfrm_state *x, struct sk_buff *skb,  netdev_features_
 
 	esp.seqno = cpu_to_be64(seq + ((u64)xo->seq.hi << 32));
 
+	if (hw_offload && encap_type == UDP_ENCAP_ESPINUDP) {
+		/* In the XFRM stack, the encapsulation protocol is set to iphdr->protocol by
+		 * setting *skb_mac_header(skb) (see esp_output_udp_encap()) where skb->mac_header
+		 * points to iphdr->protocol (see xfrm4_tunnel_encap_add()).
+		 * However, in esp_xmit(), skb->mac_header doesn't point to iphdr->protocol.
+		 * Therefore, the protocol field needs to be corrected.
+		 */
+		ip_hdr(skb)->protocol = IPPROTO_UDP;
+
+		esph->seq_no = htonl(seq);
+	}
+
 	ip_hdr(skb)->tot_len = htons(skb->len);
 	ip_send_check(ip_hdr(skb));
 

net/xfrm/xfrm_device.c

@@ -261,9 +261,9 @@ int xfrm_dev_state_add(struct net *net, struct xfrm_state *x,
 
 	is_packet_offload = xuo->flags & XFRM_OFFLOAD_PACKET;
 
-	/* We don't yet support UDP encapsulation and TFC padding. */
-	if ((!is_packet_offload && x->encap) || x->tfcpad) {
-		NL_SET_ERR_MSG(extack, "Encapsulation and TFC padding can't be offloaded");
+	/* We don't yet support TFC padding. */
+	if (x->tfcpad) {
+		NL_SET_ERR_MSG(extack, "TFC padding can't be offloaded");
 		return -EINVAL;
 	}
 

net/xfrm/xfrm_input.c

@@ -471,7 +471,8 @@ int xfrm_input(struct sk_buff *skb, int nexthdr, __be32 spi, int encap_type)
 	struct xfrm_offload *xo = xfrm_offload(skb);
 	struct sec_path *sp;
 
-	if (encap_type < 0 || (xo && xo->flags & XFRM_GRO)) {
+	if (encap_type < 0 || (xo && (xo->flags & XFRM_GRO || encap_type == 0 ||
+				      encap_type == UDP_ENCAP_ESPINUDP))) {
 		x = xfrm_input_state(skb);
 
 		if (unlikely(x->dir && x->dir != XFRM_SA_DIR_IN)) {

net/xfrm/xfrm_policy.c

@@ -3718,12 +3718,15 @@ int __xfrm_policy_check(struct sock *sk, int dir, struct sk_buff *skb,
 		pol = xfrm_in_fwd_icmp(skb, &fl, family, if_id);
 
 	if (!pol) {
+		const bool is_crypto_offload = sp &&
+			(xfrm_input_state(skb)->xso.type == XFRM_DEV_OFFLOAD_CRYPTO);
+
 		if (net->xfrm.policy_default[dir] == XFRM_USERPOLICY_BLOCK) {
 			XFRM_INC_STATS(net, LINUX_MIB_XFRMINNOPOLS);
 			return 0;
 		}
 
-		if (sp && secpath_has_nontransport(sp, 0, &xerr_idx)) {
+		if (sp && secpath_has_nontransport(sp, 0, &xerr_idx) && !is_crypto_offload) {
 			xfrm_secpath_reject(xerr_idx, skb, &fl);
 			XFRM_INC_STATS(net, LINUX_MIB_XFRMINNOPOLS);
 			return 0;