Packets received over the socket are forwarded to the user device.
Implementation is UDP only. TCP will be added by a later patch.
Note: no decryption/decapsulation exists yet, packets are forwarded as they arrive without much processing.
Signed-off-by: Antonio Quartulli antonio@openvpn.net --- drivers/net/ovpn/io.c | 66 ++++++++++++++++++++++++++- drivers/net/ovpn/io.h | 2 + drivers/net/ovpn/main.c | 8 +++- drivers/net/ovpn/ovpnstruct.h | 3 ++ drivers/net/ovpn/proto.h | 75 ++++++++++++++++++++++++++++++ drivers/net/ovpn/socket.c | 24 ++++++++++ drivers/net/ovpn/udp.c | 104 +++++++++++++++++++++++++++++++++++++++++- drivers/net/ovpn/udp.h | 3 +- 8 files changed, 281 insertions(+), 4 deletions(-)
diff --git a/drivers/net/ovpn/io.c b/drivers/net/ovpn/io.c index dfd2c90c56842374b7fb1c8bead061a76272441e..78449b52a2f8f710107d2493299c6aca9a2cb2ce 100644 --- a/drivers/net/ovpn/io.c +++ b/drivers/net/ovpn/io.c @@ -9,14 +9,78 @@
#include <linux/netdevice.h> #include <linux/skbuff.h> +#include <net/gro_cells.h> #include <net/gso.h>
-#include "io.h" #include "ovpnstruct.h" #include "peer.h" +#include "io.h" +#include "netlink.h" +#include "proto.h" #include "udp.h" #include "skb.h"
+/* 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; + + /* 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ip_summed = CHECKSUM_NONE; + + /* skb hash for transport packet no longer valid after decapsulation */ + skb_clear_hash(skb); + + /* post-decrypt scrub -- prepare to inject encapsulated packet onto the + * interface, based on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); + + skb_reset_network_header(skb); + skb_reset_transport_header(skb); + skb_probe_transport_header(skb); + skb_reset_inner_headers(skb); + + memset(skb->cb, 0, sizeof(skb->cb)); + + /* cause packet to be "received" by the interface */ + pkt_len = skb->len; + if (likely(gro_cells_receive(&peer->ovpn->gro_cells, + skb) == NET_RX_SUCCESS)) + /* update RX stats with the size of decrypted packet */ + dev_sw_netstats_rx_add(peer->ovpn->dev, pkt_len); +} + +static void ovpn_decrypt_post(struct sk_buff *skb, int ret) +{ + struct ovpn_peer *peer = ovpn_skb_cb(skb)->peer; + + if (unlikely(ret < 0)) + goto drop; + + ovpn_netdev_write(peer, skb); + /* skb is passed to upper layer - don't free it */ + skb = NULL; +drop: + if (unlikely(skb)) + dev_core_stats_rx_dropped_inc(peer->ovpn->dev); + ovpn_peer_put(peer); + kfree_skb(skb); +} + +/* pick next packet from RX queue, decrypt and forward it to the device */ +void ovpn_recv(struct ovpn_peer *peer, struct sk_buff *skb) +{ + ovpn_skb_cb(skb)->peer = peer; + ovpn_decrypt_post(skb, 0); +} + static void ovpn_encrypt_post(struct sk_buff *skb, int ret) { struct ovpn_peer *peer = ovpn_skb_cb(skb)->peer; diff --git a/drivers/net/ovpn/io.h b/drivers/net/ovpn/io.h index aa259be66441f7b0262f39da12d6c3dce0a9b24c..9667a0a470e0b4b427524fffb5b9b395007e5a2f 100644 --- a/drivers/net/ovpn/io.h +++ b/drivers/net/ovpn/io.h @@ -12,4 +12,6 @@
netdev_tx_t ovpn_net_xmit(struct sk_buff *skb, struct net_device *dev);
+void ovpn_recv(struct ovpn_peer *peer, struct sk_buff *skb); + #endif /* _NET_OVPN_OVPN_H_ */ diff --git a/drivers/net/ovpn/main.c b/drivers/net/ovpn/main.c index 4522f2f8978614c96d529f807bd2cf32a44f8216..670e66f8f750086de5d48e4708721d102c149a2e 100644 --- a/drivers/net/ovpn/main.c +++ b/drivers/net/ovpn/main.c @@ -13,6 +13,7 @@ #include <linux/inetdevice.h> //#include <linux/rcupdate.h> #include <linux/version.h> +#include <net/gro_cells.h> #include <net/ip.h> #include <net/rtnetlink.h> #include <uapi/linux/if_arp.h> @@ -45,11 +46,16 @@ static void ovpn_struct_init(struct net_device *dev, enum ovpn_mode mode)
static void ovpn_struct_free(struct net_device *net) { + struct ovpn_struct *ovpn = netdev_priv(net); + + gro_cells_destroy(&ovpn->gro_cells); }
static int ovpn_net_init(struct net_device *dev) { - return 0; + struct ovpn_struct *ovpn = netdev_priv(dev); + + return gro_cells_init(&ovpn->gro_cells, dev); }
static int ovpn_net_open(struct net_device *dev) diff --git a/drivers/net/ovpn/ovpnstruct.h b/drivers/net/ovpn/ovpnstruct.h index 25f4837b798b1a2c9b11763dfb5b44e8ec337e6f..65497ce115aa4be719ed03f89135a80b73f9ef9b 100644 --- a/drivers/net/ovpn/ovpnstruct.h +++ b/drivers/net/ovpn/ovpnstruct.h @@ -10,6 +10,7 @@ #ifndef _NET_OVPN_OVPNSTRUCT_H_ #define _NET_OVPN_OVPNSTRUCT_H_
+#include <net/gro_cells.h> #include <net/net_trackers.h> #include <uapi/linux/ovpn.h>
@@ -22,6 +23,7 @@ * @lock: protect this object * @peer: in P2P mode, this is the only remote peer * @dev_list: entry for the module wide device list + * @gro_cells: pointer to the Generic Receive Offload cell */ struct ovpn_struct { struct net_device *dev; @@ -31,6 +33,7 @@ struct ovpn_struct { spinlock_t lock; /* protect writing to the ovpn_struct object */ struct ovpn_peer __rcu *peer; struct list_head dev_list; + struct gro_cells gro_cells; };
#endif /* _NET_OVPN_OVPNSTRUCT_H_ */ diff --git a/drivers/net/ovpn/proto.h b/drivers/net/ovpn/proto.h new file mode 100644 index 0000000000000000000000000000000000000000..69604cf26bbf82539ee5cd5a7ac9c23920f555de --- /dev/null +++ b/drivers/net/ovpn/proto.h @@ -0,0 +1,75 @@ +/* SPDX-License-Identifier: GPL-2.0-only */ +/* OpenVPN data channel offload + * + * Copyright (C) 2020-2024 OpenVPN, Inc. + * + * Author: Antonio Quartulli antonio@openvpn.net + * James Yonan james@openvpn.net + */ + +#ifndef _NET_OVPN_OVPNPROTO_H_ +#define _NET_OVPN_OVPNPROTO_H_ + +#include "main.h" + +#include <linux/skbuff.h> + +/* Methods for operating on the initial command + * byte of the OpenVPN protocol. + */ + +/* packet opcode (high 5 bits) and key-id (low 3 bits) are combined in + * one byte + */ +#define OVPN_KEY_ID_MASK 0x07 +#define OVPN_OPCODE_SHIFT 3 +#define OVPN_OPCODE_MASK 0x1F +/* upper bounds on opcode and key ID */ +#define OVPN_KEY_ID_MAX (OVPN_KEY_ID_MASK + 1) +#define OVPN_OPCODE_MAX (OVPN_OPCODE_MASK + 1) +/* packet opcodes of interest to us */ +#define OVPN_DATA_V1 6 /* data channel V1 packet */ +#define OVPN_DATA_V2 9 /* data channel V2 packet */ +/* size of initial packet opcode */ +#define OVPN_OP_SIZE_V1 1 +#define OVPN_OP_SIZE_V2 4 +#define OVPN_PEER_ID_MASK 0x00FFFFFF +#define OVPN_PEER_ID_UNDEF 0x00FFFFFF +/* first byte of keepalive message */ +#define OVPN_KEEPALIVE_FIRST_BYTE 0x2a +/* first byte of exit message */ +#define OVPN_EXPLICIT_EXIT_NOTIFY_FIRST_BYTE 0x28 + +/** + * ovpn_opcode_from_skb - extract OP code from skb at specified offset + * @skb: the packet to extract the OP code from + * @offset: the offset in the data buffer where the OP code is located + * + * Note: this function assumes that the skb head was pulled enough + * to access the first byte. + * + * Return: the OP code + */ +static inline u8 ovpn_opcode_from_skb(const struct sk_buff *skb, u16 offset) +{ + u8 byte = *(skb->data + offset); + + return byte >> OVPN_OPCODE_SHIFT; +} + +/** + * ovpn_peer_id_from_skb - extract peer ID from skb at specified offset + * @skb: the packet to extract the OP code from + * @offset: the offset in the data buffer where the OP code is located + * + * Note: this function assumes that the skb head was pulled enough + * to access the first 4 bytes. + * + * Return: the peer ID. + */ +static inline u32 ovpn_peer_id_from_skb(const struct sk_buff *skb, u16 offset) +{ + return ntohl(*(__be32 *)(skb->data + offset)) & OVPN_PEER_ID_MASK; +} + +#endif /* _NET_OVPN_OVPNPROTO_H_ */ diff --git a/drivers/net/ovpn/socket.c b/drivers/net/ovpn/socket.c index 090a3232ab0ec19702110f1a90f45c7f10889f6f..964b566de69f4132806a969a455cec7f6059a0bd 100644 --- a/drivers/net/ovpn/socket.c +++ b/drivers/net/ovpn/socket.c @@ -22,6 +22,9 @@ static void ovpn_socket_detach(struct socket *sock) if (!sock) return;
+ if (sock->sk->sk_protocol == IPPROTO_UDP) + ovpn_udp_socket_detach(sock); + sockfd_put(sock); }
@@ -71,6 +74,27 @@ static int ovpn_socket_attach(struct socket *sock, struct ovpn_peer *peer) return ret; }
+/* Retrieve the corresponding ovpn object from a UDP socket + * rcu_read_lock must be held on entry + */ +struct ovpn_struct *ovpn_from_udp_sock(struct sock *sk) +{ + struct ovpn_socket *ovpn_sock; + + if (unlikely(READ_ONCE(udp_sk(sk)->encap_type) != UDP_ENCAP_OVPNINUDP)) + return NULL; + + ovpn_sock = rcu_dereference_sk_user_data(sk); + if (unlikely(!ovpn_sock)) + return NULL; + + /* make sure that sk matches our stored transport socket */ + if (unlikely(!ovpn_sock->sock || sk != ovpn_sock->sock->sk)) + return NULL; + + return ovpn_sock->ovpn; +} + /** * ovpn_socket_new - create a new socket and initialize it * @sock: the kernel socket to embed diff --git a/drivers/net/ovpn/udp.c b/drivers/net/ovpn/udp.c index d26d7566e9c8dfe91fa77f49c34fb179a9fb2239..d1e88ae83843f02d591e67a7995f2d6868720695 100644 --- a/drivers/net/ovpn/udp.c +++ b/drivers/net/ovpn/udp.c @@ -21,9 +21,95 @@ #include "bind.h" #include "io.h" #include "peer.h" +#include "proto.h" #include "socket.h" #include "udp.h"
+/** + * ovpn_udp_encap_recv - Start processing a received UDP packet. + * @sk: socket over which the packet was received + * @skb: the received packet + * + * If the first byte of the payload is DATA_V2, the packet is further processed, + * otherwise it is forwarded to the UDP stack for delivery to user space. + * + * Return: + * 0 if skb was consumed or dropped + * >0 if skb should be passed up to userspace as UDP (packet not consumed) + * <0 if skb should be resubmitted as proto -N (packet not consumed) + */ +static int ovpn_udp_encap_recv(struct sock *sk, struct sk_buff *skb) +{ + struct ovpn_peer *peer = NULL; + struct ovpn_struct *ovpn; + u32 peer_id; + u8 opcode; + + ovpn = ovpn_from_udp_sock(sk); + if (unlikely(!ovpn)) { + net_err_ratelimited("%s: cannot obtain ovpn object from UDP socket\n", + __func__); + goto drop_noovpn; + } + + /* Make sure the first 4 bytes of the skb data buffer after the UDP + * header are accessible. + * They are required to fetch the OP code, the key ID and the peer ID. + */ + if (unlikely(!pskb_may_pull(skb, sizeof(struct udphdr) + + OVPN_OP_SIZE_V2))) { + net_dbg_ratelimited("%s: packet too small\n", __func__); + goto drop; + } + + opcode = ovpn_opcode_from_skb(skb, sizeof(struct udphdr)); + if (unlikely(opcode != OVPN_DATA_V2)) { + /* DATA_V1 is not supported */ + if (opcode == OVPN_DATA_V1) + goto drop; + + /* unknown or control packet: let it bubble up to userspace */ + return 1; + } + + peer_id = ovpn_peer_id_from_skb(skb, sizeof(struct udphdr)); + /* some OpenVPN server implementations send data packets with the + * peer-id set to undef. In this case we skip the peer lookup by peer-id + * and we try with the transport address + */ + if (peer_id != OVPN_PEER_ID_UNDEF) { + peer = ovpn_peer_get_by_id(ovpn, peer_id); + if (!peer) { + net_err_ratelimited("%s: received data from unknown peer (id: %d)\n", + __func__, peer_id); + goto drop; + } + } + + if (!peer) { + /* data packet with undef peer-id */ + peer = ovpn_peer_get_by_transp_addr(ovpn, skb); + if (unlikely(!peer)) { + net_dbg_ratelimited("%s: received data with undef peer-id from unknown source\n", + __func__); + goto drop; + } + } + + /* pop off outer UDP header */ + __skb_pull(skb, sizeof(struct udphdr)); + ovpn_recv(peer, skb); + return 0; + +drop: + if (peer) + ovpn_peer_put(peer); + dev_core_stats_rx_dropped_inc(ovpn->dev); +drop_noovpn: + kfree_skb(skb); + return 0; +} + /** * ovpn_udp4_output - send IPv4 packet over udp socket * @ovpn: the openvpn instance @@ -259,8 +345,12 @@ void ovpn_udp_send_skb(struct ovpn_struct *ovpn, struct ovpn_peer *peer, */ int ovpn_udp_socket_attach(struct socket *sock, struct ovpn_struct *ovpn) { + struct udp_tunnel_sock_cfg cfg = { + .encap_type = UDP_ENCAP_OVPNINUDP, + .encap_rcv = ovpn_udp_encap_recv, + }; struct ovpn_socket *old_data; - int ret = 0; + int ret;
/* sanity check */ if (sock->sk->sk_protocol != IPPROTO_UDP) { @@ -274,6 +364,7 @@ int ovpn_udp_socket_attach(struct socket *sock, struct ovpn_struct *ovpn) if (!old_data) { /* socket is currently unused - we can take it */ rcu_read_unlock(); + setup_udp_tunnel_sock(sock_net(sock->sk), sock, &cfg); return 0; }
@@ -302,3 +393,14 @@ int ovpn_udp_socket_attach(struct socket *sock, struct ovpn_struct *ovpn)
return ret; } + +/** + * ovpn_udp_socket_detach - clean udp-tunnel status for this socket + * @sock: the socket to clean + */ +void ovpn_udp_socket_detach(struct socket *sock) +{ + struct udp_tunnel_sock_cfg cfg = { }; + + setup_udp_tunnel_sock(sock_net(sock->sk), sock, &cfg); +} diff --git a/drivers/net/ovpn/udp.h b/drivers/net/ovpn/udp.h index e60f8cd2b4ac8f910aabcf8ed546af59d6ca4be4..fecb68464896bc1228315faf268453f9005e693d 100644 --- a/drivers/net/ovpn/udp.h +++ b/drivers/net/ovpn/udp.h @@ -18,8 +18,9 @@ struct sk_buff; struct socket;
int ovpn_udp_socket_attach(struct socket *sock, struct ovpn_struct *ovpn); - +void ovpn_udp_socket_detach(struct socket *sock); void ovpn_udp_send_skb(struct ovpn_struct *ovpn, struct ovpn_peer *peer, struct sk_buff *skb); +struct ovpn_struct *ovpn_from_udp_sock(struct sock *sk);
#endif /* _NET_OVPN_UDP_H_ */