ip/l2tp: remove offset and peer-offset options

Ignore options "peer-offset" and "offset" when creating sessions. Keep
them when dumping sessions in order to avoid breaking external scripts.

"peer-offset" has always been a noop in iproute2. "offset" is now
ignored in Linux 4.16 (and was broken before that).

Signed-off-by: Guillaume Nault <g.nault@alphalink.fr>
Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>

ip/ipl2tp.c

@@ -42,8 +42,6 @@ struct l2tp_parm {
 	uint32_t peer_tunnel_id;
 	uint32_t session_id;
 	uint32_t peer_session_id;
-	uint32_t offset;
-	uint32_t peer_offset;
 	enum l2tp_encap_type encap;
 	uint16_t local_udp_port;
 	uint16_t peer_udp_port;
@@ -174,8 +172,6 @@ static int create_session(struct l2tp_parm *p)
 	if (p->reorder_timeout)
 		addattr64(&req.n, 1024, L2TP_ATTR_RECV_TIMEOUT,
 					  p->reorder_timeout);
-	if (p->offset)
-		addattr16(&req.n, 1024, L2TP_ATTR_OFFSET, p->offset);
 	if (p->cookie_len)
 		addattr_l(&req.n, 1024, L2TP_ATTR_COOKIE,
 			  p->cookie, p->cookie_len);
@@ -310,8 +306,8 @@ static void print_session(struct l2tp_data *data)
 		print_string(PRINT_FP, NULL, "%s", _SL_);
 	}
 
-	print_uint(PRINT_ANY, "offset", "  offset %u,", p->offset);
+	print_uint(PRINT_ANY, "offset", "  offset %u,", 0);
-	print_uint(PRINT_ANY, "peer_offset", " peer offset %u\n", p->peer_offset);
+	print_uint(PRINT_ANY, "peer_offset", " peer offset %u\n", 0);
 
 	if (p->cookie_len > 0)
 		print_cookie("cookie", "cookie",
@@ -362,8 +358,6 @@ static int get_response(struct nlmsghdr *n, void *arg)
 		p->pw_type = rta_getattr_u16(attrs[L2TP_ATTR_PW_TYPE]);
 	if (attrs[L2TP_ATTR_ENCAP_TYPE])
 		p->encap = rta_getattr_u16(attrs[L2TP_ATTR_ENCAP_TYPE]);
-	if (attrs[L2TP_ATTR_OFFSET])
-		p->offset = rta_getattr_u16(attrs[L2TP_ATTR_OFFSET]);
 	if (attrs[L2TP_ATTR_DATA_SEQ])
 		p->data_seq = rta_getattr_u16(attrs[L2TP_ATTR_DATA_SEQ]);
 	if (attrs[L2TP_ATTR_CONN_ID])
@@ -550,7 +544,6 @@ static void usage(void)
 		"          tunnel_id ID\n"
 		"          session_id ID peer_session_id ID\n"
 		"          [ cookie HEXSTR ] [ peer_cookie HEXSTR ]\n"
-		"          [ offset OFFSET ] [ peer_offset OFFSET ]\n"
 		"          [ seq { none | send | recv | both } ]\n"
 		"          [ l2spec_type L2SPEC ]\n"
 		"       ip l2tp del tunnel tunnel_id ID\n"
@@ -678,19 +671,11 @@ static int parse_args(int argc, char **argv, int cmd, struct l2tp_parm *p)
 				invarg("invalid option for udp6_csum_tx\n"
 						, *argv);
 		} else if (strcmp(*argv, "offset") == 0) {
-			__u8 uval;
+			fprintf(stderr, "Ignoring option \"offset\"\n");
-
 			NEXT_ARG();
-			if (get_u8(&uval, *argv, 0))
-				invarg("invalid offset\n", *argv);
-			p->offset = uval;
 		} else if (strcmp(*argv, "peer_offset") == 0) {
-			__u8 uval;
+			fprintf(stderr, "Ignoring option \"peer_offset\"\n");
-
 			NEXT_ARG();
-			if (get_u8(&uval, *argv, 0))
-				invarg("invalid offset\n", *argv);
-			p->peer_offset = uval;
 		} else if (strcmp(*argv, "cookie") == 0) {
 			int slen;
 

man/man8/ip-l2tp.8

@@ -59,12 +59,6 @@ ip-l2tp - L2TPv3 static unmanaged tunnel configuration
 .br
 .RB "[ " seq " { " none " | " send " | " recv " | " both " } ]"
 .br
-.RB "[ " offset
-.IR OFFSET
-.RB " ] [ " peer_offset
-.IR OFFSET
-.RB " ]"
-.br
 .ti -8
 .BR "ip l2tp del tunnel"
 .B tunnel_id
@@ -285,16 +279,6 @@ Default is
 .br
 Valid values are:
 .BR none ", " send ", " recv ", " both "."
-.TP
-.BI offset " OFFSET"
-sets the byte offset from the L2TP header where user data starts in
-transmitted L2TP data packets. This is hardly ever used. If set, the
-value must match the peer_offset value used at the peer. Default is 0.
-.TP
-.BI peer_offset " OFFSET"
-sets the byte offset from the L2TP header where user data starts in
-received L2TP data packets. This is hardly ever used. If set, the
-value must match the offset value used at the peer. Default is 0.
 .SS ip l2tp del session - destroy a session
 .TP
 .BI tunnel_id " ID"