[PATCH iproute2-next] ip: add OVPN device mode support

[Marco Baffo <marco@mandelbit.com>]

Allow selecting point-to-point or multi-peer mode when creating an
OVPN device.

Signed-off-by: Marco Baffo <marco@mandelbit.com>
---
 ip/Makefile           |  2 +-
 ip/iplink.c           |  2 +-
 ip/iplink_ovpn.c      | 87 +++++++++++++++++++++++++++++++++++++++++++
 man/man8/ip-link.8.in | 24 ++++++++++++
 4 files changed, 113 insertions(+), 2 deletions(-)
 create mode 100644 ip/iplink_ovpn.c

diff --git a/ip/Makefile b/ip/Makefile
index 3535ba78..978f6841 100644
--- a/ip/Makefile
+++ b/ip/Makefile
@@ -13,7 +13,7 @@ IPOBJ=ip.o ipaddress.o ipaddrlabel.o iproute.o iprule.o ipnetns.o \
     ipvrf.o iplink_xstats.o ipseg6.o iplink_netdevsim.o iplink_rmnet.o \
     ipnexthop.o ipmptcp.o iplink_bareudp.o iplink_wwan.o ipioam6.o \
     iplink_amt.o iplink_batadv.o iplink_gtp.o iplink_virt_wifi.o \
-    iplink_netkit.o ipstats.o
+    iplink_netkit.o ipstats.o iplink_ovpn.o
 
 RTMONOBJ=rtmon.o
 
diff --git a/ip/iplink.c b/ip/iplink.c
index 3f0b46c9..c6aee8b6 100644
--- a/ip/iplink.c
+++ b/ip/iplink.c
@@ -42,7 +42,7 @@ void iplink_types_usage(void)
 		"          ifb | ip6erspan | ip6gre | ip6gretap | ip6tnl |\n"
 		"          ipip | ipoib | ipvlan | ipvtap |\n"
 		"          macsec | macvlan | macvtap | netdevsim |\n"
-		"          netkit | nlmon | pfcp | rmnet | sit | team | team_slave |\n"
+		"          netkit | nlmon | ovpn | pfcp | rmnet | sit | team | team_slave |\n"
 		"          vcan | veth | vlan | vrf | vti | vxcan | vxlan | wwan |\n"
 		"          xfrm | virt_wifi }\n");
 }
diff --git a/ip/iplink_ovpn.c b/ip/iplink_ovpn.c
new file mode 100644
index 00000000..08e59526
--- /dev/null
+++ b/ip/iplink_ovpn.c
@@ -0,0 +1,87 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/*
+ * iplink_ovpn.c	OpenVPN DCO device support
+ *
+ * Author: Marco Baffo <marco@mandelbit.com>
+ *
+ */
+
+#include <stdio.h>
+#include <string.h>
+#include <linux/if_link.h>
+
+#include "utils.h"
+#include "ip_common.h"
+
+static void print_explain(FILE *f)
+{
+	fprintf(f,
+		"Usage: ... ovpn [ mode { p2p | mp } ]\n"
+		"\n"
+		"MODE := p2p | mp\n"
+		"(p2p is the default if mode is not specified)\n");
+}
+
+static int ovpn_parse_opt(struct link_util *lu, int argc, char **argv,
+			  struct nlmsghdr *n)
+{
+	while (argc > 0) {
+		if (matches(*argv, "mode") == 0) {
+			__u8 mode;
+
+			NEXT_ARG();
+			if (strcmp(*argv, "p2p") == 0)
+				mode = OVPN_MODE_P2P;
+			else if (strcmp(*argv, "mp") == 0)
+				mode = OVPN_MODE_MP;
+			else {
+				fprintf(stderr,
+					"Error: argument of \"mode\" must be either \"p2p\" or \"mp\"\n");
+				return -1;
+			}
+			addattr8(n, 1024, IFLA_OVPN_MODE, mode);
+		} else if (matches(*argv, "help") == 0) {
+			print_explain(stderr);
+			return -1;
+		} else {
+			fprintf(stderr, "ovpn: unknown option \"%s\"?\n", *argv);
+			print_explain(stderr);
+			return -1;
+		}
+		argc--;
+		argv++;
+	}
+
+	return 0;
+}
+
+static void ovpn_print_opt(struct link_util *lu, FILE *f, struct rtattr *tb[])
+{
+	__u8 value;
+
+	if (!tb || !tb[IFLA_OVPN_MODE] ||
+	    RTA_PAYLOAD(tb[IFLA_OVPN_MODE]) < sizeof(value))
+		return;
+
+	value = rta_getattr_u8(tb[IFLA_OVPN_MODE]);
+
+	const char *mode =
+		value == OVPN_MODE_P2P ? "p2p" :
+	    value == OVPN_MODE_MP ? "mp" : "unknown";
+
+	print_string(PRINT_ANY, "mode", "mode %s ", mode);
+}
+
+static void ovpn_print_help(struct link_util *lu, int argc, char **argv,
+			    FILE *f)
+{
+	print_explain(f);
+}
+
+struct link_util ovpn_link_util = {
+	.id		= "ovpn",
+	.maxattr	= IFLA_OVPN_MAX,
+	.parse_opt	= ovpn_parse_opt,
+	.print_opt	= ovpn_print_opt,
+	.print_help	= ovpn_print_help,
+};
diff --git a/man/man8/ip-link.8.in b/man/man8/ip-link.8.in
index fc7f0248..d54d2fbc 100644
--- a/man/man8/ip-link.8.in
+++ b/man/man8/ip-link.8.in
@@ -287,6 +287,7 @@ ip-link \- network device configuration
 .BR netdevsim " |"
 .BR netkit " |"
 .BR nlmon " |"
+.BR ovpn " |"
 .BR pfcp " |"
 .BR rmnet " |"
 .BR sit " |"
@@ -430,6 +431,9 @@ Link types:
 .BR nlmon
 - Netlink monitoring device
 .sp
+.BR ovpn
+- OpenVPN Data Channel Offload device
+.sp
 .BR pfcp
 - Packet Forwarding Control Protocol device
 .sp
@@ -1349,6 +1353,26 @@ the following additional arguments are supported:
 .BI  mode " MODE "
 - specifies the mode (datagram or connected) to use.
 
+.TP
+OVPN Type Support
+For a link of type
+.I OVPN
+the following additional arguments are supported:
+
+.BI "ip link add " DEVICE
+.BR "type ovpn " [ " mode " "{ " p2p " | " mp " }" " ]"
+
+.in +8
+.sp
+.BR mode " { " p2p " | " mp " }"
+- selects the OpenVPN device mode. The default,
+.BR p2p ,
+creates a point-to-point device for a single peer. The
+.B mp
+mode creates a multi-peer device.
+
+.in -8
+
 .TP
 ERSPAN Type Support
 For a link of type
-- 
2.43.0