1 files changed, 458 insertions, 0 deletions
diff --git a/drivers/net/ovpn/io.c b/drivers/net/ovpn/io.c
new file mode 100644
index 000000000000..10d8afecec55
--- /dev/null
+++ b/drivers/net/ovpn/io.c
@@ -0,0 +1,458 @@
+// SPDX-License-Identifier: GPL-2.0
+/*  OpenVPN data channel offload
+ *
+ *  Copyright (C) 2019-2025 OpenVPN, Inc.
+ *
+ *  Author:	James Yonan <james@openvpn.net>
+ *		Antonio Quartulli <antonio@openvpn.net>
+ */
+
+#include <crypto/aead.h>
+#include <linux/netdevice.h>
+#include <linux/skbuff.h>
+#include <net/gro_cells.h>
+#include <net/gso.h>
+#include <net/ip.h>
+
+#include "ovpnpriv.h"
+#include "peer.h"
+#include "io.h"
+#include "bind.h"
+#include "crypto.h"
+#include "crypto_aead.h"
+#include "netlink.h"
+#include "proto.h"
+#include "tcp.h"
+#include "udp.h"
+#include "skb.h"
+#include "socket.h"
+
+const unsigned char ovpn_keepalive_message[OVPN_KEEPALIVE_SIZE] = {
+	0x2a, 0x18, 0x7b, 0xf3, 0x64, 0x1e, 0xb4, 0xcb,
+	0x07, 0xed, 0x2d, 0x0a, 0x98, 0x1f, 0xc7, 0x48
+};
+
+/**
+ * ovpn_is_keepalive - check if skb contains a keepalive message
+ * @skb: packet to check
+ *
+ * Assumes that the first byte of skb->data is defined.
+ *
+ * Return: true if skb contains a keepalive or false otherwise
+ */
+static bool ovpn_is_keepalive(struct sk_buff *skb)
+{
+	if (*skb->data != ovpn_keepalive_message[0])
+		return false;
+
+	if (skb->len != OVPN_KEEPALIVE_SIZE)
+		return false;
+
+	if (!pskb_may_pull(skb, OVPN_KEEPALIVE_SIZE))
+		return false;
+
+	return !memcmp(skb->data, ovpn_keepalive_message, OVPN_KEEPALIVE_SIZE);
+}
+
+/* Called after decrypt to write the IP packet to the device.
+ * This method is expected to manage/free the skb.
+ */
+static void ovpn_netdev_write(struct ovpn_peer *peer, struct sk_buff *skb)
+{
+	unsigned int pkt_len;
+	int ret;
+
+	/* we can't guarantee the packet wasn't corrupted before entering the
+	 * VPN, therefore we give other layers a chance to check that
+	 */
+	skb->ip_summed = CHECKSUM_NONE;
+
+	/* skb hash for transport packet no longer valid after decapsulation */
+	skb_clear_hash(skb);
+
+	/* post-decrypt scrub -- prepare to inject encapsulated packet onto the
+	 * interface, based on __skb_tunnel_rx() in dst.h
+	 */
+	skb->dev = peer->ovpn->dev;
+	skb_set_queue_mapping(skb, 0);
+	skb_scrub_packet(skb, true);
+
+	/* network header reset in ovpn_decrypt_post() */
+	skb_reset_transport_header(skb);
+	skb_reset_inner_headers(skb);
+
+	/* cause packet to be "received" by the interface */
+	pkt_len = skb->len;
+	ret = gro_cells_receive(&peer->ovpn->gro_cells, skb);
+	if (likely(ret == NET_RX_SUCCESS)) {
+		/* update RX stats with the size of decrypted packet */
+		ovpn_peer_stats_increment_rx(&peer->vpn_stats, pkt_len);
+		dev_dstats_rx_add(peer->ovpn->dev, pkt_len);
+	}
+}
+
+void ovpn_decrypt_post(void *data, int ret)
+{
+	struct ovpn_crypto_key_slot *ks;
+	unsigned int payload_offset = 0;
+	struct sk_buff *skb = data;
+	struct ovpn_socket *sock;
+	struct ovpn_peer *peer;
+	__be16 proto;
+	__be32 *pid;
+
+	/* crypto is happening asynchronously. this function will be called
+	 * again later by the crypto callback with a proper return code
+	 */
+	if (unlikely(ret == -EINPROGRESS))
+		return;
+
+	payload_offset = ovpn_skb_cb(skb)->payload_offset;
+	ks = ovpn_skb_cb(skb)->ks;
+	peer = ovpn_skb_cb(skb)->peer;
+
+	/* crypto is done, cleanup skb CB and its members */
+	kfree(ovpn_skb_cb(skb)->iv);
+	kfree(ovpn_skb_cb(skb)->sg);
+	aead_request_free(ovpn_skb_cb(skb)->req);
+
+	if (unlikely(ret < 0))
+		goto drop;
+
+	/* PID sits after the op */
+	pid = (__force __be32 *)(skb->data + OVPN_OPCODE_SIZE);
+	ret = ovpn_pktid_recv(&ks->pid_recv, ntohl(*pid), 0);
+	if (unlikely(ret < 0)) {
+		net_err_ratelimited("%s: PKT ID RX error for peer %u: %d\n",
+				    netdev_name(peer->ovpn->dev), peer->id,
+				    ret);
+		goto drop;
+	}
+
+	/* keep track of last received authenticated packet for keepalive */
+	WRITE_ONCE(peer->last_recv, ktime_get_real_seconds());
+
+	rcu_read_lock();
+	sock = rcu_dereference(peer->sock);
+	if (sock && sock->sock->sk->sk_protocol == IPPROTO_UDP)
+		/* check if this peer changed local or remote endpoint */
+		ovpn_peer_endpoints_update(peer, skb);
+	rcu_read_unlock();
+
+	/* point to encapsulated IP packet */
+	__skb_pull(skb, payload_offset);
+
+	/* check if this is a valid datapacket that has to be delivered to the
+	 * ovpn interface
+	 */
+	skb_reset_network_header(skb);
+	proto = ovpn_ip_check_protocol(skb);
+	if (unlikely(!proto)) {
+		/* check if null packet */
+		if (unlikely(!pskb_may_pull(skb, 1))) {
+			net_info_ratelimited("%s: NULL packet received from peer %u\n",
+					     netdev_name(peer->ovpn->dev),
+					     peer->id);
+			goto drop;
+		}
+
+		if (ovpn_is_keepalive(skb)) {
+			net_dbg_ratelimited("%s: ping received from peer %u\n",
+					    netdev_name(peer->ovpn->dev),
+					    peer->id);
+			/* we drop the packet, but this is not a failure */
+			consume_skb(skb);
+			goto drop_nocount;
+		}
+
+		net_info_ratelimited("%s: unsupported protocol received from peer %u\n",
+				     netdev_name(peer->ovpn->dev), peer->id);
+		goto drop;
+	}
+	skb->protocol = proto;
+
+	/* perform Reverse Path Filtering (RPF) */
+	if (unlikely(!ovpn_peer_check_by_src(peer->ovpn, skb, peer))) {
+		if (skb->protocol == htons(ETH_P_IPV6))
+			net_dbg_ratelimited("%s: RPF dropped packet from peer %u, src: %pI6c\n",
+					    netdev_name(peer->ovpn->dev),
+					    peer->id, &ipv6_hdr(skb)->saddr);
+		else
+			net_dbg_ratelimited("%s: RPF dropped packet from peer %u, src: %pI4\n",
+					    netdev_name(peer->ovpn->dev),
+					    peer->id, &ip_hdr(skb)->saddr);
+		goto drop;
+	}
+
+	ovpn_netdev_write(peer, skb);
+	/* skb is passed to upper layer - don't free it */
+	skb = NULL;
+drop:
+	if (unlikely(skb))
+		dev_dstats_rx_dropped(peer->ovpn->dev);
+	kfree_skb(skb);
+drop_nocount:
+	if (likely(peer))
+		ovpn_peer_put(peer);
+	if (likely(ks))
+		ovpn_crypto_key_slot_put(ks);
+}
+
+/* RX path entry point: decrypt packet and forward it to the device */
+void ovpn_recv(struct ovpn_peer *peer, struct sk_buff *skb)
+{
+	struct ovpn_crypto_key_slot *ks;
+	u8 key_id;
+
+	ovpn_peer_stats_increment_rx(&peer->link_stats, skb->len);
+
+	/* get the key slot matching the key ID in the received packet */
+	key_id = ovpn_key_id_from_skb(skb);
+	ks = ovpn_crypto_key_id_to_slot(&peer->crypto, key_id);
+	if (unlikely(!ks)) {
+		net_info_ratelimited("%s: no available key for peer %u, key-id: %u\n",
+				     netdev_name(peer->ovpn->dev), peer->id,
+				     key_id);
+		dev_dstats_rx_dropped(peer->ovpn->dev);
+		kfree_skb(skb);
+		ovpn_peer_put(peer);
+		return;
+	}
+
+	memset(ovpn_skb_cb(skb), 0, sizeof(struct ovpn_cb));
+	ovpn_decrypt_post(skb, ovpn_aead_decrypt(peer, ks, skb));
+}
+
+void ovpn_encrypt_post(void *data, int ret)
+{
+	struct ovpn_crypto_key_slot *ks;
+	struct sk_buff *skb = data;
+	struct ovpn_socket *sock;
+	struct ovpn_peer *peer;
+	unsigned int orig_len;
+
+	/* encryption is happening asynchronously. This function will be
+	 * called later by the crypto callback with a proper return value
+	 */
+	if (unlikely(ret == -EINPROGRESS))
+		return;
+
+	ks = ovpn_skb_cb(skb)->ks;
+	peer = ovpn_skb_cb(skb)->peer;
+
+	/* crypto is done, cleanup skb CB and its members */
+	kfree(ovpn_skb_cb(skb)->iv);
+	kfree(ovpn_skb_cb(skb)->sg);
+	aead_request_free(ovpn_skb_cb(skb)->req);
+
+	if (unlikely(ret == -ERANGE)) {
+		/* we ran out of IVs and we must kill the key as it can't be
+		 * use anymore
+		 */
+		netdev_warn(peer->ovpn->dev,
+			    "killing key %u for peer %u\n", ks->key_id,
+			    peer->id);
+		if (ovpn_crypto_kill_key(&peer->crypto, ks->key_id))
+			/* let userspace know so that a new key must be negotiated */
+			ovpn_nl_key_swap_notify(peer, ks->key_id);
+
+		goto err;
+	}
+
+	if (unlikely(ret < 0))
+		goto err;
+
+	skb_mark_not_on_list(skb);
+	orig_len = skb->len;
+
+	rcu_read_lock();
+	sock = rcu_dereference(peer->sock);
+	if (unlikely(!sock))
+		goto err_unlock;
+
+	switch (sock->sock->sk->sk_protocol) {
+	case IPPROTO_UDP:
+		ovpn_udp_send_skb(peer, sock->sock, skb);
+		break;
+	case IPPROTO_TCP:
+		ovpn_tcp_send_skb(peer, sock->sock, skb);
+		break;
+	default:
+		/* no transport configured yet */
+		goto err_unlock;
+	}
+
+	ovpn_peer_stats_increment_tx(&peer->link_stats, orig_len);
+	/* keep track of last sent packet for keepalive */
+	WRITE_ONCE(peer->last_sent, ktime_get_real_seconds());
+	/* skb passed down the stack - don't free it */
+	skb = NULL;
+err_unlock:
+	rcu_read_unlock();
+err:
+	if (unlikely(skb))
+		dev_dstats_tx_dropped(peer->ovpn->dev);
+	if (likely(peer))
+		ovpn_peer_put(peer);
+	if (likely(ks))
+		ovpn_crypto_key_slot_put(ks);
+	kfree_skb(skb);
+}
+
+static bool ovpn_encrypt_one(struct ovpn_peer *peer, struct sk_buff *skb)
+{
+	struct ovpn_crypto_key_slot *ks;
+
+	/* get primary key to be used for encrypting data */
+	ks = ovpn_crypto_key_slot_primary(&peer->crypto);
+	if (unlikely(!ks))
+		return false;
+
+	/* take a reference to the peer because the crypto code may run async.
+	 * ovpn_encrypt_post() will release it upon completion
+	 */
+	if (unlikely(!ovpn_peer_hold(peer))) {
+		DEBUG_NET_WARN_ON_ONCE(1);
+		ovpn_crypto_key_slot_put(ks);
+		return false;
+	}
+
+	memset(ovpn_skb_cb(skb), 0, sizeof(struct ovpn_cb));
+	ovpn_encrypt_post(skb, ovpn_aead_encrypt(peer, ks, skb));
+	return true;
+}
+
+/* send skb to connected peer, if any */
+static void ovpn_send(struct ovpn_priv *ovpn, struct sk_buff *skb,
+		      struct ovpn_peer *peer)
+{
+	struct sk_buff *curr, *next;
+
+	/* this might be a GSO-segmented skb list: process each skb
+	 * independently
+	 */
+	skb_list_walk_safe(skb, curr, next) {
+		if (unlikely(!ovpn_encrypt_one(peer, curr))) {
+			dev_dstats_tx_dropped(ovpn->dev);
+			kfree_skb(curr);
+		}
+	}
+
+	ovpn_peer_put(peer);
+}
+
+/* Send user data to the network
+ */
+netdev_tx_t ovpn_net_xmit(struct sk_buff *skb, struct net_device *dev)
+{
+	struct ovpn_priv *ovpn = netdev_priv(dev);
+	struct sk_buff *segments, *curr, *next;
+	struct sk_buff_head skb_list;
+	struct ovpn_peer *peer;
+	__be16 proto;
+	int ret;
+
+	/* reset netfilter state */
+	nf_reset_ct(skb);
+
+	/* verify IP header size in network packet */
+	proto = ovpn_ip_check_protocol(skb);
+	if (unlikely(!proto || skb->protocol != proto))
+		goto drop;
+
+	if (skb_is_gso(skb)) {
+		segments = skb_gso_segment(skb, 0);
+		if (IS_ERR(segments)) {
+			ret = PTR_ERR(segments);
+			net_err_ratelimited("%s: cannot segment payload packet: %d\n",
+					    netdev_name(dev), ret);
+			goto drop;
+		}
+
+		consume_skb(skb);
+		skb = segments;
+	}
+
+	/* from this moment on, "skb" might be a list */
+
+	__skb_queue_head_init(&skb_list);
+	skb_list_walk_safe(skb, curr, next) {
+		skb_mark_not_on_list(curr);
+
+		curr = skb_share_check(curr, GFP_ATOMIC);
+		if (unlikely(!curr)) {
+			net_err_ratelimited("%s: skb_share_check failed for payload packet\n",
+					    netdev_name(dev));
+			dev_dstats_tx_dropped(ovpn->dev);
+			continue;
+		}
+
+		__skb_queue_tail(&skb_list, curr);
+	}
+	skb_list.prev->next = NULL;
+
+	/* retrieve peer serving the destination IP of this packet */
+	peer = ovpn_peer_get_by_dst(ovpn, skb);
+	if (unlikely(!peer)) {
+		switch (skb->protocol) {
+		case htons(ETH_P_IP):
+			net_dbg_ratelimited("%s: no peer to send data to dst=%pI4\n",
+					    netdev_name(ovpn->dev),
+					    &ip_hdr(skb)->daddr);
+			break;
+		case htons(ETH_P_IPV6):
+			net_dbg_ratelimited("%s: no peer to send data to dst=%pI6c\n",
+					    netdev_name(ovpn->dev),
+					    &ipv6_hdr(skb)->daddr);
+			break;
+		}
+		goto drop;
+	}
+	/* dst was needed for peer selection - it can now be dropped */
+	skb_dst_drop(skb);
+
+	ovpn_peer_stats_increment_tx(&peer->vpn_stats, skb->len);
+	ovpn_send(ovpn, skb_list.next, peer);
+
+	return NETDEV_TX_OK;
+
+drop:
+	dev_dstats_tx_dropped(ovpn->dev);
+	skb_tx_error(skb);
+	kfree_skb_list(skb);
+	return NETDEV_TX_OK;
+}
+
+/**
+ * ovpn_xmit_special - encrypt and transmit an out-of-band message to peer
+ * @peer: peer to send the message to
+ * @data: message content
+ * @len: message length
+ *
+ * Assumes that caller holds a reference to peer, which will be
+ * passed to ovpn_send()
+ */
+void ovpn_xmit_special(struct ovpn_peer *peer, const void *data,
+		       const unsigned int len)
+{
+	struct ovpn_priv *ovpn;
+	struct sk_buff *skb;
+
+	ovpn = peer->ovpn;
+	if (unlikely(!ovpn)) {
+		ovpn_peer_put(peer);
+		return;
+	}
+
+	skb = alloc_skb(256 + len, GFP_ATOMIC);
+	if (unlikely(!skb)) {
+		ovpn_peer_put(peer);
+		return;
+	}
+
+	skb_reserve(skb, 128);
+	skb->priority = TC_PRIO_BESTEFFORT;
+	__skb_put_data(skb, data, len);
+
+	ovpn_send(ovpn, skb, peer);
+}