lib/libnetlink: update rtnl_talk to support malloc buff at run time

This is an update for 460c03f3f3cc ("iplink: double the buffer size also in
iplink_get()"). After update, we will not need to double the buffer size
every time when VFs number increased.

With call like rtnl_talk(&rth, &req.n, NULL, 0), we can simply remove the
length parameter.

With call like rtnl_talk(&rth, nlh, nlh, sizeof(req), I add a new variable
answer to avoid overwrite data in nlh, because it may has more info after
nlh. also this will avoid nlh buffer not enough issue.

We need to free answer after using.

Signed-off-by: Hangbin Liu <liuhangbin@gmail.com>
Signed-off-by: Phil Sutter <phil@nwl.cc>

37 files changed, 220 insertions, 177 deletions

diff --git a/bridge/fdb.c b/bridge/fdb.c
index e5cebf9b..807914f0 100644
--- a/bridge/fdb.c
+++ b/bridge/fdb.c
@@ -535,7 +535,7 @@ static int fdb_modify(int cmd, int flags, int argc, char **argv)
 		return -1;
 	}
 
-	if (rtnl_talk(&rth, &req.n, NULL, 0) < 0)
+	if (rtnl_talk(&rth, &req.n, NULL) < 0)
 		return -1;
 
 	return 0;
diff --git a/bridge/link.c b/bridge/link.c
index d3a211ef..70aaa01b 100644
--- a/bridge/link.c
+++ b/bridge/link.c
@@ -439,7 +439,7 @@ static int brlink_modify(int argc, char **argv)
 		addattr_nest_end(&req.n, nest);
 	}
 
-	if (rtnl_talk(&rth, &req.n, NULL, 0) < 0)
+	if (rtnl_talk(&rth, &req.n, NULL) < 0)
 		return -1;
 
 	return 0;
diff --git a/bridge/mdb.c b/bridge/mdb.c
index 748091b8..f38e326e 100644
--- a/bridge/mdb.c
+++ b/bridge/mdb.c
@@ -440,7 +440,7 @@ static int mdb_modify(int cmd, int flags, int argc, char **argv)
 	entry.vid = vid;
 	addattr_l(&req.n, sizeof(req), MDBA_SET_ENTRY, &entry, sizeof(entry));
 
-	if (rtnl_talk(&rth, &req.n, NULL, 0) < 0)
+	if (rtnl_talk(&rth, &req.n, NULL) < 0)
 		return -1;
 
 	return 0;
diff --git a/bridge/vlan.c b/bridge/vlan.c
index ebcdacee..5d683595 100644
--- a/bridge/vlan.c
+++ b/bridge/vlan.c
@@ -133,7 +133,7 @@ static int vlan_modify(int cmd, int argc, char **argv)
 
 	addattr_nest_end(&req.n, afspec);
 
-	if (rtnl_talk(&rth, &req.n, NULL, 0) < 0)
+	if (rtnl_talk(&rth, &req.n, NULL) < 0)
 		return -1;
 
 	return 0;
diff --git a/genl/ctrl.c b/genl/ctrl.c
index 448988eb..a6d31b04 100644
--- a/genl/ctrl.c
+++ b/genl/ctrl.c
@@ -55,6 +55,7 @@ int genl_ctrl_resolve_family(const char *family)
 	};
 	struct nlmsghdr *nlh = &req.n;
 	struct genlmsghdr *ghdr = &req.g;
+	struct nlmsghdr *answer = NULL;
 
 	if (rtnl_open_byproto(&rth, 0, NETLINK_GENERIC) < 0) {
 		fprintf(stderr, "Cannot open generic netlink socket\n");
@@ -63,19 +64,19 @@ int genl_ctrl_resolve_family(const char *family)
 
 	addattr_l(nlh, 128, CTRL_ATTR_FAMILY_NAME, family, strlen(family) + 1);
 
-	if (rtnl_talk(&rth, nlh, nlh, sizeof(req)) < 0) {
+	if (rtnl_talk(&rth, nlh, &answer) < 0) {
 		fprintf(stderr, "Error talking to the kernel\n");
 		goto errout;
 	}
 
 	{
 		struct rtattr *tb[CTRL_ATTR_MAX + 1];
-		int len = nlh->nlmsg_len;
+		int len = answer->nlmsg_len;
 		struct rtattr *attrs;
 
-		if (nlh->nlmsg_type !=  GENL_ID_CTRL) {
+		if (answer->nlmsg_type !=  GENL_ID_CTRL) {
 			fprintf(stderr, "Not a controller message, nlmsg_len=%d "
-				"nlmsg_type=0x%x\n", nlh->nlmsg_len, nlh->nlmsg_type);
+				"nlmsg_type=0x%x\n", answer->nlmsg_len, answer->nlmsg_type);
 			goto errout;
 		}
 
@@ -88,10 +89,11 @@ int genl_ctrl_resolve_family(const char *family)
 
 		if (len < 0) {
 			fprintf(stderr, "wrong controller message len %d\n", len);
+			free(answer);
 			return -1;
 		}
 
-		attrs = (struct rtattr *) ((char *) ghdr + GENL_HDRLEN);
+		attrs = (struct rtattr *) ((char *) answer + NLMSG_LENGTH(GENL_HDRLEN));
 		parse_rtattr(tb, CTRL_ATTR_MAX, attrs, len);
 
 		if (tb[CTRL_ATTR_FAMILY_ID] == NULL) {
@@ -103,6 +105,7 @@ int genl_ctrl_resolve_family(const char *family)
 	}
 
 errout:
+	free(answer);
 	rtnl_close(&rth);
 	return ret;
 }
@@ -299,6 +302,7 @@ static int ctrl_list(int cmd, int argc, char **argv)
 		.g.cmd = CTRL_CMD_GETFAMILY,
 	};
 	struct nlmsghdr *nlh = &req.n;
+	struct nlmsghdr *answer = NULL;
 
 	if (rtnl_open_byproto(&rth, 0, NETLINK_GENERIC) < 0) {
 		fprintf(stderr, "Cannot open generic netlink socket\n");
@@ -331,12 +335,12 @@ static int ctrl_list(int cmd, int argc, char **argv)
 			goto ctrl_done;
 		}
 
-		if (rtnl_talk(&rth, nlh, nlh, sizeof(req)) < 0) {
+		if (rtnl_talk(&rth, nlh, &answer) < 0) {
 			fprintf(stderr, "Error talking to the kernel\n");
 			goto ctrl_done;
 		}
 
-		if (print_ctrl2(NULL, nlh, (void *) stdout) < 0) {
+		if (print_ctrl2(NULL, answer, (void *) stdout) < 0) {
 			fprintf(stderr, "Dump terminated\n");
 			goto ctrl_done;
 		}
@@ -358,6 +362,7 @@ static int ctrl_list(int cmd, int argc, char **argv)
 
 	ret = 0;
 ctrl_done:
+	free(answer);
 	rtnl_close(&rth);
 	return ret;
 }
diff --git a/include/libnetlink.h b/include/libnetlink.h
index 69257f0e..77b62605 100644
--- a/include/libnetlink.h
+++ b/include/libnetlink.h
@@ -93,13 +93,13 @@ int rtnl_dump_filter_nc(struct rtnl_handle *rth,
 #define rtnl_dump_filter(rth, filter, arg) \
 	rtnl_dump_filter_nc(rth, filter, arg, 0)
 int rtnl_talk(struct rtnl_handle *rtnl, struct nlmsghdr *n,
-	      struct nlmsghdr *answer, size_t len)
+	      struct nlmsghdr **answer)
 	__attribute__((warn_unused_result));
 int rtnl_talk_extack(struct rtnl_handle *rtnl, struct nlmsghdr *n,
-	      struct nlmsghdr *answer, size_t len, nl_ext_ack_fn_t errfn)
+	      struct nlmsghdr **answer, nl_ext_ack_fn_t errfn)
 	__attribute__((warn_unused_result));
 int rtnl_talk_suppress_rtnl_errmsg(struct rtnl_handle *rtnl, struct nlmsghdr *n,
-				   struct nlmsghdr *answer, size_t len)
+				   struct nlmsghdr **answer)
 	__attribute__((warn_unused_result));
 int rtnl_send(struct rtnl_handle *rth, const void *buf, int)
 	__attribute__((warn_unused_result));
diff --git a/ip/ipaddress.c b/ip/ipaddress.c
index 9e9a7e0a..c8db769e 100644
--- a/ip/ipaddress.c
+++ b/ip/ipaddress.c
@@ -1838,7 +1838,7 @@ static int restore_handler(const struct sockaddr_nl *nl,
 
 	ll_init_map(&rth);
 
-	ret = rtnl_talk(&rth, n, n, sizeof(*n));
+	ret = rtnl_talk(&rth, n, NULL);
 	if ((ret < 0) && (errno == EEXIST))
 		ret = 0;
 
@@ -2534,7 +2534,7 @@ static int ipaddr_modify(int cmd, int flags, int argc, char **argv)
 		return -1;
 	}
 
-	if (rtnl_talk(&rth, &req.n, NULL, 0) < 0)
+	if (rtnl_talk(&rth, &req.n, NULL) < 0)
 		return -2;
 
 	return 0;
diff --git a/ip/ipaddrlabel.c b/ip/ipaddrlabel.c
index 1d324dac..6ea9bfff 100644
--- a/ip/ipaddrlabel.c
+++ b/ip/ipaddrlabel.c
@@ -176,7 +176,7 @@ static int ipaddrlabel_modify(int cmd, int argc, char **argv)
 	if (req.ifal.ifal_family == AF_UNSPEC)
 		req.ifal.ifal_family = AF_INET6;
 
-	if (rtnl_talk(&rth, &req.n, NULL, 0) < 0)
+	if (rtnl_talk(&rth, &req.n, NULL) < 0)
 		return -2;
 
 	return 0;
@@ -203,7 +203,7 @@ static int flush_addrlabel(const struct sockaddr_nl *who, struct nlmsghdr *n, vo
 		if (rtnl_open(&rth2, 0) < 0)
 			return -1;
 
-		if (rtnl_talk(&rth2, n, NULL, 0) < 0)
+		if (rtnl_talk(&rth2, n, NULL) < 0)
 			return -2;
 
 		rtnl_close(&rth2);
diff --git a/ip/ipfou.c b/ip/ipfou.c
index 00dbe150..23000dc6 100644
--- a/ip/ipfou.c
+++ b/ip/ipfou.c
@@ -116,7 +116,7 @@ static int do_add(int argc, char **argv)
 
 	fou_parse_opt(argc, argv, &req.n, true);
 
-	if (rtnl_talk(&genl_rth, &req.n, NULL, 0) < 0)
+	if (rtnl_talk(&genl_rth, &req.n, NULL) < 0)
 		return -2;
 
 	return 0;
@@ -128,7 +128,7 @@ static int do_del(int argc, char **argv)
 
 	fou_parse_opt(argc, argv, &req.n, false);
 
-	if (rtnl_talk(&genl_rth, &req.n, NULL, 0) < 0)
+	if (rtnl_talk(&genl_rth, &req.n, NULL) < 0)
 		return -2;
 
 	return 0;
diff --git a/ip/ipila.c b/ip/ipila.c
index 843cc165..0403fc42 100644
--- a/ip/ipila.c
+++ b/ip/ipila.c
@@ -220,7 +220,7 @@ static int do_add(int argc, char **argv)
 
 	ila_parse_opt(argc, argv, &req.n, true);
 
-	if (rtnl_talk(&genl_rth, &req.n, NULL, 0) < 0)
+	if (rtnl_talk(&genl_rth, &req.n, NULL) < 0)
 		return -2;
 
 	return 0;
@@ -232,7 +232,7 @@ static int do_del(int argc, char **argv)
 
 	ila_parse_opt(argc, argv, &req.n, false);
 
-	if (rtnl_talk(&genl_rth, &req.n, NULL, 0) < 0)
+	if (rtnl_talk(&genl_rth, &req.n, NULL) < 0)
 		return -2;
 
 	return 0;
diff --git a/ip/ipl2tp.c b/ip/ipl2tp.c
index 1e37b175..7c5ed313 100644
--- a/ip/ipl2tp.c
+++ b/ip/ipl2tp.c
@@ -129,7 +129,7 @@ static int create_tunnel(struct l2tp_parm *p)
 			addattr(&req.n, 1024, L2TP_ATTR_UDP_ZERO_CSUM6_RX);
 	}
 
-	if (rtnl_talk(&genl_rth, &req.n, NULL, 0) < 0)
+	if (rtnl_talk(&genl_rth, &req.n, NULL) < 0)
 		return -2;
 
 	return 0;
@@ -142,7 +142,7 @@ static int delete_tunnel(struct l2tp_parm *p)
 
 	addattr32(&req.n, 128, L2TP_ATTR_CONN_ID, p->tunnel_id);
 
-	if (rtnl_talk(&genl_rth, &req.n, NULL, 0) < 0)
+	if (rtnl_talk(&genl_rth, &req.n, NULL) < 0)
 		return -2;
 
 	return 0;
@@ -185,7 +185,7 @@ static int create_session(struct l2tp_parm *p)
 	if (p->ifname)
 		addattrstrz(&req.n, 1024, L2TP_ATTR_IFNAME, p->ifname);
 
-	if (rtnl_talk(&genl_rth, &req.n, NULL, 0) < 0)
+	if (rtnl_talk(&genl_rth, &req.n, NULL) < 0)
 		return -2;
 
 	return 0;
@@ -198,7 +198,7 @@ static int delete_session(struct l2tp_parm *p)
 
 	addattr32(&req.n, 1024, L2TP_ATTR_CONN_ID, p->tunnel_id);
 	addattr32(&req.n, 1024, L2TP_ATTR_SESSION_ID, p->session_id);
-	if (rtnl_talk(&genl_rth, &req.n, NULL, 0) < 0)
+	if (rtnl_talk(&genl_rth, &req.n, NULL) < 0)
 		return -2;
 
 	return 0;
diff --git a/ip/iplink.c b/ip/iplink.c
index 6a96ea9f..0daca3f9 100644
--- a/ip/iplink.c
+++ b/ip/iplink.c
@@ -249,19 +249,26 @@ static int nl_get_ll_addr_len(unsigned int dev_index)
 			.ifi_index = dev_index,
 		}
 	};
+	struct nlmsghdr *answer;
 	struct rtattr *tb[IFLA_MAX+1];
 
-	if (rtnl_talk(&rth, &req.n, &req.n, sizeof(req)) < 0)
+	if (rtnl_talk(&rth, &req.n, &answer) < 0)
 		return -1;
 
-	len = req.n.nlmsg_len - NLMSG_LENGTH(sizeof(req.i));
-	if (len < 0)
+	len = answer->nlmsg_len - NLMSG_LENGTH(sizeof(struct ifinfomsg));
+	if (len < 0) {
+		free(answer);
 		return -1;
+	}
 
-	parse_rtattr_flags(tb, IFLA_MAX, IFLA_RTA(&req.i), len, NLA_F_NESTED);
-	if (!tb[IFLA_ADDRESS])
+	parse_rtattr_flags(tb, IFLA_MAX, IFLA_RTA(NLMSG_DATA(answer)),
+			   len, NLA_F_NESTED);
+	if (!tb[IFLA_ADDRESS]) {
+		free(answer);
 		return -1;
+	}
 
+	free(answer);
 	return RTA_PAYLOAD(tb[IFLA_ADDRESS]);
 }
 
@@ -916,7 +923,7 @@ static int iplink_modify(int cmd, unsigned int flags, int argc, char **argv)
 
 			req.i.ifi_index = 0;
 			addattr32(&req.n, sizeof(req), IFLA_GROUP, group);
-			if (rtnl_talk(&rth, &req.n, NULL, 0) < 0)
+			if (rtnl_talk(&rth, &req.n, NULL) < 0)
 				return -2;
 			return 0;
 		}
@@ -1006,7 +1013,7 @@ static int iplink_modify(int cmd, unsigned int flags, int argc, char **argv)
 		return -1;
 	}
 
-	if (rtnl_talk(&rth, &req.n, NULL, 0) < 0)
+	if (rtnl_talk(&rth, &req.n, NULL) < 0)
 		return -2;
 
 	return 0;
@@ -1020,10 +1027,7 @@ int iplink_get(unsigned int flags, char *name, __u32 filt_mask)
 		.n.nlmsg_type = RTM_GETLINK,
 		.i.ifi_family = preferred_family,
 	};
-	struct {
-		struct nlmsghdr n;
-		char buf[32768];
-	} answer;
+	struct nlmsghdr *answer;
 
 	if (name) {
 		addattr_l(&req.n, sizeof(req),
@@ -1031,21 +1035,17 @@ int iplink_get(unsigned int flags, char *name, __u32 filt_mask)
 	}
 	addattr32(&req.n, sizeof(req), IFLA_EXT_MASK, filt_mask);
 
-	if (rtnl_talk(&rth, &req.n, &answer.n, sizeof(answer)) < 0)
-		return -2;
-	if (answer.n.nlmsg_len > sizeof(answer.buf)) {
-		fprintf(stderr, "Message truncated from %u to %lu\n",
-			answer.n.nlmsg_len, sizeof(answer.buf));
+	if (rtnl_talk(&rth, &req.n, &answer) < 0)
 		return -2;
-	}
 
 	open_json_object(NULL);
 	if (brief)
-		print_linkinfo_brief(NULL, &answer.n, stdout, NULL);
+		print_linkinfo_brief(NULL, answer, stdout, NULL);
 	else
-		print_linkinfo(NULL, &answer.n, stdout);
+		print_linkinfo(NULL, answer, stdout);
 	close_json_object();
 
+	free(answer);
 	return 0;
 }
 
diff --git a/ip/iplink_vrf.c b/ip/iplink_vrf.c
index 7a1bb5e7..e9dd0df9 100644
--- a/ip/iplink_vrf.c
+++ b/ip/iplink_vrf.c
@@ -119,10 +119,7 @@ __u32 ipvrf_get_table(const char *name)
 			.ifi_family  = preferred_family,
 		},
 	};
-	struct {
-		struct nlmsghdr n;
-		char buf[8192];
-	} answer;
+	struct nlmsghdr *answer;
 	struct rtattr *tb[IFLA_MAX+1];
 	struct rtattr *li[IFLA_INFO_MAX+1];
 	struct rtattr *vrf_attr[IFLA_VRF_MAX + 1];
@@ -132,8 +129,7 @@ __u32 ipvrf_get_table(const char *name)
 
 	addattr_l(&req.n, sizeof(req), IFLA_IFNAME, name, strlen(name) + 1);
 
-	if (rtnl_talk_suppress_rtnl_errmsg(&rth, &req.n,
-					   &answer.n, sizeof(answer)) < 0) {
+	if (rtnl_talk_suppress_rtnl_errmsg(&rth, &req.n, &answer) < 0) {
 		/* special case "default" vrf to be the main table */
 		if (errno == ENODEV && !strcmp(name, "default"))
 			if (rtnl_rttable_a2n(&tb_id, "main"))
@@ -143,25 +139,25 @@ __u32 ipvrf_get_table(const char *name)
 		return tb_id;
 	}
 
-	ifi = NLMSG_DATA(&answer.n);
-	len = answer.n.nlmsg_len - NLMSG_LENGTH(sizeof(*ifi));
+	ifi = NLMSG_DATA(answer);
+	len = answer->nlmsg_len - NLMSG_LENGTH(sizeof(*ifi));
 	if (len < 0) {
 		fprintf(stderr, "BUG: Invalid response to link query.\n");
-		return 0;
+		goto out;
 	}
 
 	parse_rtattr(tb, IFLA_MAX, IFLA_RTA(ifi), len);
 
 	if (!tb[IFLA_LINKINFO])
-		return 0;
+		goto out;
 
 	parse_rtattr_nested(li, IFLA_INFO_MAX, tb[IFLA_LINKINFO]);
 
 	if (!li[IFLA_INFO_KIND] || !li[IFLA_INFO_DATA])
-		return 0;
+		goto out;
 
 	if (strcmp(RTA_DATA(li[IFLA_INFO_KIND]), "vrf"))
-		return 0;
+		goto out;
 
 	parse_rtattr_nested(vrf_attr, IFLA_VRF_MAX, li[IFLA_INFO_DATA]);
 	if (vrf_attr[IFLA_VRF_TABLE])
@@ -170,6 +166,8 @@ __u32 ipvrf_get_table(const char *name)
 	if (!tb_id)
 		fprintf(stderr, "BUG: VRF %s is missing table id\n", name);
 
+out:
+	free(answer);
 	return tb_id;
 }
 
@@ -189,10 +187,7 @@ int name_is_vrf(const char *name)
 			.ifi_family  = preferred_family,
 		},
 	};
-	struct {
-		struct nlmsghdr n;
-		char buf[8192];
-	} answer;
+	struct nlmsghdr *answer;
 	struct rtattr *tb[IFLA_MAX+1];
 	struct rtattr *li[IFLA_INFO_MAX+1];
 	struct ifinfomsg *ifi;
@@ -200,29 +195,30 @@ int name_is_vrf(const char *name)
 
 	addattr_l(&req.n, sizeof(req), IFLA_IFNAME, name, strlen(name) + 1);
 
-	if (rtnl_talk_suppress_rtnl_errmsg(&rth, &req.n,
-					   &answer.n, sizeof(answer)) < 0)
+	if (rtnl_talk_suppress_rtnl_errmsg(&rth, &req.n, &answer) < 0)
 		return 0;
 
-	ifi = NLMSG_DATA(&answer.n);
-	len = answer.n.nlmsg_len - NLMSG_LENGTH(sizeof(*ifi));
+	ifi = NLMSG_DATA(answer);
+	len = answer->nlmsg_len - NLMSG_LENGTH(sizeof(*ifi));
 	if (len < 0) {
 		fprintf(stderr, "BUG: Invalid response to link query.\n");
-		return 0;
+		goto out;
 	}
 
 	parse_rtattr(tb, IFLA_MAX, IFLA_RTA(ifi), len);
 
 	if (!tb[IFLA_LINKINFO])
-		return 0;
+		goto out;
 
 	parse_rtattr_nested(li, IFLA_INFO_MAX, tb[IFLA_LINKINFO]);
 
 	if (!li[IFLA_INFO_KIND])
-		return 0;
+		goto out;
 
 	if (strcmp(RTA_DATA(li[IFLA_INFO_KIND]), "vrf"))
-		return 0;
+		goto out;
 
+out:
+	free(answer);
 	return ifi->ifi_index;
 }
diff --git a/ip/ipmacsec.c b/ip/ipmacsec.c
index ecc371a5..345a7073 100644
--- a/ip/ipmacsec.c
+++ b/ip/ipmacsec.c
@@ -421,7 +421,7 @@ static int do_modify_nl(enum cmd c, enum macsec_nl_commands cmd, int ifindex,
 	addattr_nest_end(&req.n, attr_sa);
 
 talk:
-	if (rtnl_talk(&genl_rth, &req.n, NULL, 0) < 0)
+	if (rtnl_talk(&genl_rth, &req.n, NULL) < 0)
 		return -2;
 
 	return 0;
diff --git a/ip/ipneigh.c b/ip/ipneigh.c
index 9c38a60d..32f2d553 100644
--- a/ip/ipneigh.c
+++ b/ip/ipneigh.c
@@ -184,7 +184,7 @@ static int ipneigh_modify(int cmd, int flags, int argc, char **argv)
 		return -1;
 	}
 
-	if (rtnl_talk(&rth, &req.n, NULL, 0) < 0)
+	if (rtnl_talk(&rth, &req.n, NULL) < 0)
 		exit(2);
 
 	return 0;
diff --git a/ip/ipnetns.c b/ip/ipnetns.c
index afb4978a..bc70997e 100644
--- a/ip/ipnetns.c
+++ b/ip/ipnetns.c
@@ -95,12 +95,13 @@ static int get_netnsid_from_name(const char *name)
 		struct nlmsghdr n;
 		struct rtgenmsg g;
 		char            buf[1024];
-	} answer, req = {
+	} req = {
 		.n.nlmsg_len = NLMSG_LENGTH(sizeof(struct rtgenmsg)),
 		.n.nlmsg_flags = NLM_F_REQUEST,
 		.n.nlmsg_type = RTM_GETNSID,
 		.g.rtgen_family = AF_UNSPEC,
 	};
+	struct nlmsghdr *answer;
 	struct rtattr *tb[NETNSA_MAX + 1];
 	struct rtgenmsg *rthdr;
 	int len, fd;
@@ -110,26 +111,30 @@ static int get_netnsid_from_name(const char *name)
 		return fd;
 
 	addattr32(&req.n, 1024, NETNSA_FD, fd);
-	if (rtnl_talk(&rtnsh, &req.n, &answer.n, sizeof(answer)) < 0) {
+	if (rtnl_talk(&rtnsh, &req.n, &answer) < 0) {
 		close(fd);
 		return -2;
 	}
 	close(fd);
 
 	/* Validate message and parse attributes */
-	if (answer.n.nlmsg_type == NLMSG_ERROR)
-		return -1;
+	if (answer->nlmsg_type == NLMSG_ERROR)
+		goto err_out;
 
-	rthdr = NLMSG_DATA(&answer.n);
-	len = answer.n.nlmsg_len - NLMSG_SPACE(sizeof(*rthdr));
+	rthdr = NLMSG_DATA(answer);
+	len = answer->nlmsg_len - NLMSG_SPACE(sizeof(*rthdr));
 	if (len < 0)
-		return -1;
+		goto err_out;
 
 	parse_rtattr(tb, NETNSA_MAX, NETNS_RTA(rthdr), len);
 
-	if (tb[NETNSA_NSID])
+	if (tb[NETNSA_NSID]) {
+		free(answer);
 		return rta_getattr_u32(tb[NETNSA_NSID]);
+	}
 
+err_out:
+	free(answer);
 	return -1;
 }
 
@@ -689,7 +694,7 @@ static int set_netnsid_from_name(const char *name, int nsid)
 
 	addattr32(&req.n, 1024, NETNSA_FD, fd);
 	addattr32(&req.n, 1024, NETNSA_NSID, nsid);
-	if (rtnl_talk(&rth, &req.n, NULL, 0) < 0)
+	if (rtnl_talk(&rth, &req.n, NULL) < 0)
 		err = -2;
 
 	close(fd);
diff --git a/ip/ipntable.c b/ip/ipntable.c
index 88236ce0..2f72c989 100644
--- a/ip/ipntable.c
+++ b/ip/ipntable.c
@@ -304,7 +304,7 @@ static int ipntable_modify(int cmd, int flags, int argc, char **argv)
 			  RTA_PAYLOAD(parms_rta));
 	}
 
-	if (rtnl_talk(&rth, &req.n, NULL, 0) < 0)
+	if (rtnl_talk(&rth, &req.n, NULL) < 0)
 		exit(2);
 
 	return 0;
diff --git a/ip/iproute.c b/ip/iproute.c
index e81bc05e..531af776 100644
--- a/ip/iproute.c
+++ b/ip/iproute.c
@@ -1300,7 +1300,7 @@ static int iproute_modify(int cmd, unsigned int flags, int argc, char **argv)
 	if (!type_ok && req.r.rtm_family == AF_MPLS)
 		req.r.rtm_type = RTN_UNICAST;
 
-	if (rtnl_talk(&rth, &req.n, NULL, 0) < 0)
+	if (rtnl_talk(&rth, &req.n, NULL) < 0)
 		return -2;
 
 	return 0;
@@ -1680,6 +1680,7 @@ static int iproute_get(int argc, char **argv)
 	};
 	char  *idev = NULL;
 	char  *odev = NULL;
+	struct nlmsghdr *answer;
 	int connected = 0;
 	int fib_match = 0;
 	int from_ok = 0;
@@ -1800,26 +1801,29 @@ static int iproute_get(int argc, char **argv)
 	if (fib_match)
 		req.r.rtm_flags |= RTM_F_FIB_MATCH;
 
-	if (rtnl_talk(&rth, &req.n, &req.n, sizeof(req)) < 0)
+	if (rtnl_talk(&rth, &req.n, &answer) < 0)
 		return -2;
 
 	if (connected && !from_ok) {
-		struct rtmsg *r = NLMSG_DATA(&req.n);
-		int len = req.n.nlmsg_len;
+		struct rtmsg *r = NLMSG_DATA(answer);
+		int len = answer->nlmsg_len;
 		struct rtattr *tb[RTA_MAX+1];
 
-		if (print_route(NULL, &req.n, (void *)stdout) < 0) {
+		if (print_route(NULL, answer, (void *)stdout) < 0) {
 			fprintf(stderr, "An error :-)\n");
+			free(answer);
 			return -1;
 		}
 
-		if (req.n.nlmsg_type != RTM_NEWROUTE) {
+		if (answer->nlmsg_type != RTM_NEWROUTE) {
 			fprintf(stderr, "Not a route?\n");
+			free(answer);
 			return -1;
 		}
 		len -= NLMSG_LENGTH(sizeof(*r));
 		if (len < 0) {
 			fprintf(stderr, "Wrong len %d\n", len);
+			free(answer);
 			return -1;
 		}
 
@@ -1830,6 +1834,7 @@ static int iproute_get(int argc, char **argv)
 			r->rtm_src_len = 8*RTA_PAYLOAD(tb[RTA_PREFSRC]);
 		} else if (!tb[RTA_SRC]) {
 			fprintf(stderr, "Failed to connect the route\n");
+			free(answer);
 			return -1;
 		}
 		if (!odev && tb[RTA_OIF])
@@ -1843,15 +1848,18 @@ static int iproute_get(int argc, char **argv)
 		req.n.nlmsg_flags = NLM_F_REQUEST;
 		req.n.nlmsg_type = RTM_GETROUTE;
 
-		if (rtnl_talk(&rth, &req.n, &req.n, sizeof(req)) < 0)
+		free(answer);
+		if (rtnl_talk(&rth, &req.n, &answer) < 0)
 			return -2;
 	}
 
-	if (print_route(NULL, &req.n, (void *)stdout) < 0) {
+	if (print_route(NULL, answer, (void *)stdout) < 0) {
 		fprintf(stderr, "An error :-)\n");
+		free(answer);
 		return -1;
 	}
 
+	free(answer);
 	return 0;
 }
 
@@ -1895,7 +1903,7 @@ restore:
 
 	ll_init_map(&rth);
 
-	ret = rtnl_talk(&rth, n, n, sizeof(*n));
+	ret = rtnl_talk(&rth, n, NULL);
 	if ((ret < 0) && (errno == EEXIST))
 		ret = 0;
 
diff --git a/ip/iprule.c b/ip/iprule.c
index 36c57fa7..201d3bdc 100644
--- a/ip/iprule.c
+++ b/ip/iprule.c
@@ -393,7 +393,7 @@ static int flush_rule(const struct sockaddr_nl *who, struct nlmsghdr *n,
 		if (rtnl_open(&rth2, 0) < 0)
 			return -1;
 
-		if (rtnl_talk(&rth2, n, NULL, 0) < 0)
+		if (rtnl_talk(&rth2, n, NULL) < 0)
 			return -2;
 
 		rtnl_close(&rth2);
@@ -555,7 +555,7 @@ static int restore_handler(const struct sockaddr_nl *nl,
 
 	ll_init_map(&rth);
 
-	ret = rtnl_talk(&rth, n, n, sizeof(*n));
+	ret = rtnl_talk(&rth, n, NULL);
 	if ((ret < 0) && (errno == EEXIST))
 		ret = 0;
 
@@ -766,7 +766,7 @@ static int iprule_modify(int cmd, int argc, char **argv)
 	if (!table_ok && cmd == RTM_NEWRULE)
 		req.r.rtm_table = RT_TABLE_MAIN;
 
-	if (rtnl_talk(&rth, &req.n, NULL, 0) < 0)
+	if (rtnl_talk(&rth, &req.n, NULL) < 0)
 		return -2;
 
 	return 0;
diff --git a/ip/ipseg6.c b/ip/ipseg6.c
index a8f5c691..461a3c1c 100644
--- a/ip/ipseg6.c
+++ b/ip/ipseg6.c
@@ -125,6 +125,7 @@ static int process_msg(const struct sockaddr_nl *who, struct nlmsghdr *n,
 static int seg6_do_cmd(void)
 {
 	SEG6_REQUEST(req, 1024, opts.cmd, NLM_F_REQUEST);
+	struct nlmsghdr *answer;
 	int repl = 0, dump = 0;
 
 	if (genl_family < 0) {
@@ -163,15 +164,16 @@ static int seg6_do_cmd(void)
 	}
 
 	if (!repl && !dump) {
-		if (rtnl_talk(&grth, &req.n, NULL, 0) < 0)
+		if (rtnl_talk(&grth, &req.n, NULL) < 0)
 			return -1;
 	} else if (repl) {
-		if (rtnl_talk(&grth, &req.n, &req.n, sizeof(req)) < 0)
+		if (rtnl_talk(&grth, &req.n, &answer) < 0)
 			return -2;
-		if (process_msg(NULL, &req.n, stdout) < 0) {
+		if (process_msg(NULL, answer, stdout) < 0) {
 			fprintf(stderr, "Error parsing reply\n");
 			exit(1);
 		}
+		free(answer);
 	} else {
 		req.n.nlmsg_flags |= NLM_F_DUMP;
 		req.n.nlmsg_seq = grth.dump = ++grth.seq;
diff --git a/ip/iptoken.c b/ip/iptoken.c
index 1869f764..0528bad7 100644
--- a/ip/iptoken.c
+++ b/ip/iptoken.c
@@ -166,7 +166,7 @@ static int iptoken_set(int argc, char **argv, bool delete)
 	addattr_nest_end(&req.n, afs6);
 	addattr_nest_end(&req.n, afs);
 
-	if (rtnl_talk(&rth, &req.n, NULL, 0) < 0)
+	if (rtnl_talk(&rth, &req.n, NULL) < 0)
 		return -2;
 
 	return 0;
diff --git a/ip/link_gre.c b/ip/link_gre.c
index 9ea2970c..35782caa 100644
--- a/ip/link_gre.c
+++ b/ip/link_gre.c
@@ -68,7 +68,6 @@ static int gre_parse_opt(struct link_util *lu, int argc, char **argv,
 	struct {
 		struct nlmsghdr n;
 		struct ifinfomsg i;
-		char buf[16384];
 	} req = {
 		.n.nlmsg_len = NLMSG_LENGTH(sizeof(*ifi)),
 		.n.nlmsg_flags = NLM_F_REQUEST,
@@ -76,6 +75,7 @@ static int gre_parse_opt(struct link_util *lu, int argc, char **argv,
 		.i.ifi_family = preferred_family,
 		.i.ifi_index = ifi->ifi_index,
 	};
+	struct nlmsghdr *answer = NULL;
 	struct rtattr *tb[IFLA_MAX + 1];
 	struct rtattr *linkinfo[IFLA_INFO_MAX+1];
 	struct rtattr *greinfo[IFLA_GRE_MAX + 1];
@@ -100,19 +100,20 @@ static int gre_parse_opt(struct link_util *lu, int argc, char **argv,
 	__u32 erspan_idx = 0;
 
 	if (!(n->nlmsg_flags & NLM_F_CREATE)) {
-		if (rtnl_talk(&rth, &req.n, &req.n, sizeof(req)) < 0) {
+		if (rtnl_talk(&rth, &req.n, &answer) < 0) {
 get_failed:
 			fprintf(stderr,
 				"Failed to get existing tunnel info.\n");
+			free(answer);
 			return -1;
 		}
 
-		len = req.n.nlmsg_len;
+		len = answer->nlmsg_len;
 		len -= NLMSG_LENGTH(sizeof(*ifi));
 		if (len < 0)
 			goto get_failed;
 
-		parse_rtattr(tb, IFLA_MAX, IFLA_RTA(&req.i), len);
+		parse_rtattr(tb, IFLA_MAX, IFLA_RTA(NLMSG_DATA(answer)), len);
 
 		if (!tb[IFLA_LINKINFO])
 			goto get_failed;
@@ -177,6 +178,8 @@ get_failed:
 
 		if (greinfo[IFLA_GRE_ERSPAN_INDEX])
 			erspan_idx = rta_getattr_u32(greinfo[IFLA_GRE_ERSPAN_INDEX]);
+
+		free(answer);
 	}
 
 	while (argc > 0) {
diff --git a/ip/link_gre6.c b/ip/link_gre6.c
index 7d07932a..2eedec85 100644
--- a/ip/link_gre6.c
+++ b/ip/link_gre6.c
@@ -78,7 +78,6 @@ static int gre_parse_opt(struct link_util *lu, int argc, char **argv,
 	struct {
 		struct nlmsghdr n;
 		struct ifinfomsg i;
-		char buf[1024];
 	} req = {
 		.n.nlmsg_len = NLMSG_LENGTH(sizeof(*ifi)),
 		.n.nlmsg_flags = NLM_F_REQUEST,
@@ -86,6 +85,7 @@ static int gre_parse_opt(struct link_util *lu, int argc, char **argv,
 		.i.ifi_family = preferred_family,
 		.i.ifi_index = ifi->ifi_index,
 	};
+	struct nlmsghdr *answer = NULL;
 	struct rtattr *tb[IFLA_MAX + 1];
 	struct rtattr *linkinfo[IFLA_INFO_MAX+1];
 	struct rtattr *greinfo[IFLA_GRE_MAX + 1];
@@ -108,19 +108,20 @@ static int gre_parse_opt(struct link_util *lu, int argc, char **argv,
 	__u32 fwmark = 0;
 
 	if (!(n->nlmsg_flags & NLM_F_CREATE)) {
-		if (rtnl_talk(&rth, &req.n, &req.n, sizeof(req)) < 0) {
+		if (rtnl_talk(&rth, &req.n, &answer) < 0) {
 get_failed:
 			fprintf(stderr,
 				"Failed to get existing tunnel info.\n");
+			free(answer);
 			return -1;
 		}
 
-		len = req.n.nlmsg_len;
+		len = answer->nlmsg_len;
 		len -= NLMSG_LENGTH(sizeof(*ifi));
 		if (len < 0)
 			goto get_failed;
 
-		parse_rtattr(tb, IFLA_MAX, IFLA_RTA(&req.i), len);
+		parse_rtattr(tb, IFLA_MAX, IFLA_RTA(NLMSG_DATA(answer)), len);
 
 		if (!tb[IFLA_LINKINFO])
 			goto get_failed;
@@ -180,6 +181,8 @@ get_failed:
 
 		if (greinfo[IFLA_GRE_FWMARK])
 			fwmark = rta_getattr_u32(greinfo[IFLA_GRE_FWMARK]);
+
+		free(answer);
 	}
 
 	while (argc > 0) {
diff --git a/ip/link_ip6tnl.c b/ip/link_ip6tnl.c
index a4199006..2f8c3f34 100644
--- a/ip/link_ip6tnl.c
+++ b/ip/link_ip6tnl.c
@@ -75,7 +75,6 @@ static int ip6tunnel_parse_opt(struct link_util *lu, int argc, char **argv,
 	struct {
 		struct nlmsghdr n;
 		struct ifinfomsg i;
-		char buf[2048];
 	} req = {
 		.n.nlmsg_len = NLMSG_LENGTH(sizeof(*ifi)),
 		.n.nlmsg_flags = NLM_F_REQUEST,
@@ -83,6 +82,7 @@ static int ip6tunnel_parse_opt(struct link_util *lu, int argc, char **argv,
 		.i.ifi_family = preferred_family,
 		.i.ifi_index = ifi->ifi_index,
 	};
+	struct nlmsghdr *answer = NULL;
 	struct rtattr *tb[IFLA_MAX + 1];
 	struct rtattr *linkinfo[IFLA_INFO_MAX+1];
 	struct rtattr *iptuninfo[IFLA_IPTUN_MAX + 1];
@@ -103,19 +103,20 @@ static int ip6tunnel_parse_opt(struct link_util *lu, int argc, char **argv,
 	__u32 fwmark = 0;
 
 	if (!(n->nlmsg_flags & NLM_F_CREATE)) {
-		if (rtnl_talk(&rth, &req.n, &req.n, sizeof(req)) < 0) {
+		if (rtnl_talk(&rth, &req.n, &answer) < 0) {
 get_failed:
 			fprintf(stderr,
 				"Failed to get existing tunnel info.\n");
+			free(answer);
 			return -1;
 		}
 
-		len = req.n.nlmsg_len;
+		len = answer->nlmsg_len;
 		len -= NLMSG_LENGTH(sizeof(*ifi));
 		if (len < 0)
 			goto get_failed;
 
-		parse_rtattr(tb, IFLA_MAX, IFLA_RTA(&req.i), len);
+		parse_rtattr(tb, IFLA_MAX, IFLA_RTA(NLMSG_DATA(answer)), len);
 
 		if (!tb[IFLA_LINKINFO])
 			goto get_failed;
@@ -158,6 +159,8 @@ get_failed:
 
 		if (iptuninfo[IFLA_IPTUN_FWMARK])
 			fwmark = rta_getattr_u32(iptuninfo[IFLA_IPTUN_FWMARK]);
+
+		free(answer);
 	}
 
 	while (argc > 0) {
diff --git a/ip/link_iptnl.c b/ip/link_iptnl.c
index 6a725e91..4940b8b0 100644
--- a/ip/link_iptnl.c
+++ b/ip/link_iptnl.c
@@ -76,7 +76,6 @@ static int iptunnel_parse_opt(struct link_util *lu, int argc, char **argv,
 	struct {
 		struct nlmsghdr n;
 		struct ifinfomsg i;
-		char buf[2048];
 	} req = {
 		.n.nlmsg_len = NLMSG_LENGTH(sizeof(*ifi)),
 		.n.nlmsg_flags = NLM_F_REQUEST,
@@ -84,6 +83,7 @@ static int iptunnel_parse_opt(struct link_util *lu, int argc, char **argv,
 		.i.ifi_family = preferred_family,
 		.i.ifi_index = ifi->ifi_index,
 	};
+	struct nlmsghdr *answer = NULL;
 	struct rtattr *tb[IFLA_MAX + 1];
 	struct rtattr *linkinfo[IFLA_INFO_MAX+1];
 	struct rtattr *iptuninfo[IFLA_IPTUN_MAX + 1];
@@ -108,19 +108,20 @@ static int iptunnel_parse_opt(struct link_util *lu, int argc, char **argv,
 	__u32 fwmark = 0;
 
 	if (!(n->nlmsg_flags & NLM_F_CREATE)) {
-		if (rtnl_talk(&rth, &req.n, &req.n, sizeof(req)) < 0) {
+		if (rtnl_talk(&rth, &req.n, &answer) < 0) {
 get_failed:
 			fprintf(stderr,
 				"Failed to get existing tunnel info.\n");
+			free(answer);
 			return -1;
 		}
 
-		len = req.n.nlmsg_len;
+		len = answer->nlmsg_len;
 		len -= NLMSG_LENGTH(sizeof(*ifi));
 		if (len < 0)
 			goto get_failed;
 
-		parse_rtattr(tb, IFLA_MAX, IFLA_RTA(&req.i), len);
+		parse_rtattr(tb, IFLA_MAX, IFLA_RTA(NLMSG_DATA(answer)), len);
 
 		if (!tb[IFLA_LINKINFO])
 			goto get_failed;
@@ -188,6 +189,7 @@ get_failed:
 		if (iptuninfo[IFLA_IPTUN_FWMARK])
 			fwmark = rta_getattr_u32(iptuninfo[IFLA_IPTUN_FWMARK]);
 
+		free(answer);
 	}
 
 	while (argc > 0) {
diff --git a/ip/link_vti.c b/ip/link_vti.c
index 8bd4d900..07ac94e7 100644
--- a/ip/link_vti.c
+++ b/ip/link_vti.c
@@ -53,7 +53,6 @@ static int vti_parse_opt(struct link_util *lu, int argc, char **argv,
 	struct {
 		struct nlmsghdr n;
 		struct ifinfomsg i;
-		char buf[1024];
 	} req = {
 		.n.nlmsg_len = NLMSG_LENGTH(sizeof(*ifi)),
 		.n.nlmsg_flags = NLM_F_REQUEST,
@@ -61,6 +60,7 @@ static int vti_parse_opt(struct link_util *lu, int argc, char **argv,
 		.i.ifi_family = preferred_family,
 		.i.ifi_index = ifi->ifi_index,
 	};
+	struct nlmsghdr *answer = NULL;
 	struct rtattr *tb[IFLA_MAX + 1];
 	struct rtattr *linkinfo[IFLA_INFO_MAX+1];
 	struct rtattr *vtiinfo[IFLA_VTI_MAX + 1];
@@ -73,19 +73,20 @@ static int vti_parse_opt(struct link_util *lu, int argc, char **argv,
 	int len;
 
 	if (!(n->nlmsg_flags & NLM_F_CREATE)) {
-		if (rtnl_talk(&rth, &req.n, &req.n, sizeof(req)) < 0) {
+		if (rtnl_talk(&rth, &req.n, &answer) < 0) {
 get_failed:
 			fprintf(stderr,
 				"Failed to get existing tunnel info.\n");
+			free(answer);
 			return -1;
 		}
 
-		len = req.n.nlmsg_len;
+		len = answer->nlmsg_len;
 		len -= NLMSG_LENGTH(sizeof(*ifi));
 		if (len < 0)
 			goto get_failed;
 
-		parse_rtattr(tb, IFLA_MAX, IFLA_RTA(&req.i), len);
+		parse_rtattr(tb, IFLA_MAX, IFLA_RTA(NLMSG_DATA(answer)), len);
 
 		if (!tb[IFLA_LINKINFO])
 			goto get_failed;
@@ -115,6 +116,8 @@ get_failed:
 
 		if (vtiinfo[IFLA_VTI_FWMARK])
 			fwmark = rta_getattr_u32(vtiinfo[IFLA_VTI_FWMARK]);
+
+		free(answer);
 	}
 
 	while (argc > 0) {
diff --git a/ip/link_vti6.c b/ip/link_vti6.c
index 8198d468..6d08bfe0 100644
--- a/ip/link_vti6.c
+++ b/ip/link_vti6.c
@@ -48,7 +48,6 @@ static int vti6_parse_opt(struct link_util *lu, int argc, char **argv,
 	struct {
 		struct nlmsghdr n;
 		struct ifinfomsg i;
-		char buf[1024];
 	} req = {
 		.n.nlmsg_len = NLMSG_LENGTH(sizeof(*ifi)),
 		.n.nlmsg_flags = NLM_F_REQUEST,
@@ -56,6 +55,7 @@ static int vti6_parse_opt(struct link_util *lu, int argc, char **argv,
 		.i.ifi_family = preferred_family,
 		.i.ifi_index = ifi->ifi_index,
 	};
+	struct nlmsghdr *answer = NULL;
 	struct rtattr *tb[IFLA_MAX + 1];
 	struct rtattr *linkinfo[IFLA_INFO_MAX+1];
 	struct rtattr *vtiinfo[IFLA_VTI_MAX + 1];
@@ -68,19 +68,20 @@ static int vti6_parse_opt(struct link_util *lu, int argc, char **argv,
 	int len;
 
 	if (!(n->nlmsg_flags & NLM_F_CREATE)) {
-		if (rtnl_talk(&rth, &req.n, &req.n, sizeof(req)) < 0) {
+		if (rtnl_talk(&rth, &req.n, &answer) < 0) {
 get_failed:
 			fprintf(stderr,
 				"Failed to get existing tunnel info.\n");
+			free(answer);
 			return -1;
 		}
 
-		len = req.n.nlmsg_len;
+		len = answer->nlmsg_len;
 		len -= NLMSG_LENGTH(sizeof(*ifi));
 		if (len < 0)
 			goto get_failed;
 
-		parse_rtattr(tb, IFLA_MAX, IFLA_RTA(&req.i), len);
+		parse_rtattr(tb, IFLA_MAX, IFLA_RTA(NLMSG_DATA(answer)), len);
 
 		if (!tb[IFLA_LINKINFO])
 			goto get_failed;
@@ -110,6 +111,8 @@ get_failed:
 
 		if (vtiinfo[IFLA_VTI_FWMARK])
 			fwmark = rta_getattr_u32(vtiinfo[IFLA_VTI_FWMARK]);
+
+		free(answer);
 	}
 
 	while (argc > 0) {
diff --git a/ip/tcp_metrics.c b/ip/tcp_metrics.c
index 8972acd0..3f9790e8 100644
--- a/ip/tcp_metrics.c
+++ b/ip/tcp_metrics.c
@@ -306,6 +306,7 @@ static int process_msg(const struct sockaddr_nl *who, struct nlmsghdr *n,
 static int tcpm_do_cmd(int cmd, int argc, char **argv)
 {
 	TCPM_REQUEST(req, 1024, TCP_METRICS_CMD_GET, NLM_F_REQUEST);
+	struct nlmsghdr *answer;
 	int atype = -1, stype = -1;
 	int ack;
 
@@ -457,15 +458,16 @@ static int tcpm_do_cmd(int cmd, int argc, char **argv)
 	}
 
 	if (ack) {
-		if (rtnl_talk(&grth, &req.n, NULL, 0) < 0)
+		if (rtnl_talk(&grth, &req.n, NULL) < 0)
 			return -2;
 	} else if (atype >= 0) {
-		if (rtnl_talk(&grth, &req.n, &req.n, sizeof(req)) < 0)
+		if (rtnl_talk(&grth, &req.n, &answer) < 0)
 			return -2;
-		if (process_msg(NULL, &req.n, stdout) < 0) {
+		if (process_msg(NULL, answer, stdout) < 0) {
 			fprintf(stderr, "Dump terminated\n");
 			exit(1);
 		}
+		free(answer);
 	} else {
 		req.n.nlmsg_seq = grth.dump = ++grth.seq;
 		if (rtnl_send(&grth, &req, req.n.nlmsg_len) < 0) {
diff --git a/ip/xfrm_policy.c b/ip/xfrm_policy.c
index de689c4d..98460a07 100644
--- a/ip/xfrm_policy.c
+++ b/ip/xfrm_policy.c
@@ -386,7 +386,7 @@ static int xfrm_policy_modify(int cmd, unsigned int flags, int argc, char **argv
 	if (req.xpinfo.sel.family == AF_UNSPEC)
 		req.xpinfo.sel.family = AF_INET;
 
-	if (rtnl_talk(&rth, &req.n, NULL, 0) < 0)
+	if (rtnl_talk(&rth, &req.n, NULL) < 0)
 		exit(2);
 
 	rtnl_close(&rth);
@@ -548,7 +548,7 @@ int xfrm_policy_print(const struct sockaddr_nl *who, struct nlmsghdr *n,
 }
 
 static int xfrm_policy_get_or_delete(int argc, char **argv, int delete,
-				     void *res_nlbuf, size_t res_size)
+				     struct nlmsghdr **answer)
 {
 	struct rtnl_handle rth;
 	struct {
@@ -659,7 +659,7 @@ static int xfrm_policy_get_or_delete(int argc, char **argv, int delete,
 			  (void *)&ctx, ctx.sctx.len);
 	}
 
-	if (rtnl_talk(&rth, &req.n, res_nlbuf, res_size) < 0)
+	if (rtnl_talk(&rth, &req.n, answer) < 0)
 		exit(2);
 
 	rtnl_close(&rth);
@@ -669,21 +669,21 @@ static int xfrm_policy_get_or_delete(int argc, char **argv, int delete,
 
 static int xfrm_policy_delete(int argc, char **argv)
 {
-	return xfrm_policy_get_or_delete(argc, argv, 1, NULL, 0);
+	return xfrm_policy_get_or_delete(argc, argv, 1, NULL);
 }
 
 static int xfrm_policy_get(int argc, char **argv)
 {
-	char buf[NLMSG_BUF_SIZE] = {};
-	struct nlmsghdr *n = (struct nlmsghdr *)buf;
+	struct nlmsghdr *n = NULL;
 
-	xfrm_policy_get_or_delete(argc, argv, 0, n, sizeof(buf));
+	xfrm_policy_get_or_delete(argc, argv, 0, &n);
 
 	if (xfrm_policy_print(NULL, n, (void *)stdout) < 0) {
 		fprintf(stderr, "An error :-)\n");
 		exit(1);
 	}
 
+	free(n);
 	return 0;
 }
 
@@ -1049,7 +1049,7 @@ static int xfrm_spd_setinfo(int argc, char **argv)
 	if (rtnl_open_byproto(&rth, 0, NETLINK_XFRM) < 0)
 		exit(1);
 
-	if (rtnl_talk(&rth, &req.n, NULL, 0) < 0)
+	if (rtnl_talk(&rth, &req.n, NULL) < 0)
 		exit(2);
 
 	rtnl_close(&rth);
@@ -1063,22 +1063,23 @@ static int xfrm_spd_getinfo(int argc, char **argv)
 	struct {
 		struct nlmsghdr			n;
 		__u32				flags;
-		char				ans[128];
 	} req = {
 		.n.nlmsg_len = NLMSG_LENGTH(sizeof(__u32)),
 		.n.nlmsg_flags = NLM_F_REQUEST,
 		.n.nlmsg_type = XFRM_MSG_GETSPDINFO,
 		.flags = 0XFFFFFFFF,
 	};
+	struct nlmsghdr *answer;
 
 	if (rtnl_open_byproto(&rth, 0, NETLINK_XFRM) < 0)
 		exit(1);
 
-	if (rtnl_talk(&rth, &req.n, &req.n, sizeof(req)) < 0)
+	if (rtnl_talk(&rth, &req.n, &answer) < 0)
 		exit(2);
 
-	print_spdinfo(&req.n, (void *)stdout);
+	print_spdinfo(answer, (void *)stdout);
 
+	free(answer);
 	rtnl_close(&rth);
 
 	return 0;
@@ -1123,7 +1124,7 @@ static int xfrm_policy_flush(int argc, char **argv)
 	if (show_stats > 1)
 		fprintf(stderr, "Flush policy\n");
 
-	if (rtnl_talk(&rth, &req.n, NULL, 0) < 0)
+	if (rtnl_talk(&rth, &req.n, NULL) < 0)
 		exit(2);
 
 	rtnl_close(&rth);
diff --git a/ip/xfrm_state.c b/ip/xfrm_state.c
index 99fdec23..3e20d6ed 100644
--- a/ip/xfrm_state.c
+++ b/ip/xfrm_state.c
@@ -726,7 +726,7 @@ static int xfrm_state_modify(int cmd, unsigned int flags, int argc, char **argv)
 	if (req.xsinfo.family == AF_UNSPEC)
 		req.xsinfo.family = AF_INET;
 
-	if (rtnl_talk(&rth, &req.n, NULL, 0) < 0)
+	if (rtnl_talk(&rth, &req.n, NULL) < 0)
 		exit(2);
 
 	rtnl_close(&rth);
@@ -757,8 +757,7 @@ static int xfrm_state_allocspi(int argc, char **argv)
 	char *minp = NULL;
 	char *maxp = NULL;
 	struct xfrm_mark mark = {0, 0};
-	char res_buf[NLMSG_BUF_SIZE] = {};
-	struct nlmsghdr *res_n = (struct nlmsghdr *)res_buf;
+	struct nlmsghdr *answer;
 
 	while (argc > 0) {
 		if (strcmp(*argv, "mode") == 0) {
@@ -858,14 +857,15 @@ static int xfrm_state_allocspi(int argc, char **argv)
 		req.xspi.info.family = AF_INET;
 
 
-	if (rtnl_talk(&rth, &req.n, res_n, sizeof(res_buf)) < 0)
+	if (rtnl_talk(&rth, &req.n, &answer) < 0)
 		exit(2);
 
-	if (xfrm_state_print(NULL, res_n, (void *)stdout) < 0) {
+	if (xfrm_state_print(NULL, answer, (void *)stdout) < 0) {
 		fprintf(stderr, "An error :-)\n");
 		exit(1);
 	}
 
+	free(answer);
 	rtnl_close(&rth);
 
 	return 0;
@@ -1046,19 +1046,20 @@ static int xfrm_state_get_or_delete(int argc, char **argv, int delete)
 		req.xsid.family = AF_INET;
 
 	if (delete) {
-		if (rtnl_talk(&rth, &req.n, NULL, 0) < 0)
+		if (rtnl_talk(&rth, &req.n, NULL) < 0)
 			exit(2);
 	} else {
-		char buf[NLMSG_BUF_SIZE] = {};
-		struct nlmsghdr *res_n = (struct nlmsghdr *)buf;
+		struct nlmsghdr *answer;
 
-		if (rtnl_talk(&rth, &req.n, res_n, sizeof(req)) < 0)
+		if (rtnl_talk(&rth, &req.n, &answer) < 0)
 			exit(2);
 
-		if (xfrm_state_print(NULL, res_n, (void *)stdout) < 0) {
+		if (xfrm_state_print(NULL, answer, (void *)stdout) < 0) {
 			fprintf(stderr, "An error :-)\n");
 			exit(1);
 		}
+
+		free(answer);
 	}
 
 	rtnl_close(&rth);
@@ -1314,22 +1315,23 @@ static int xfrm_sad_getinfo(int argc, char **argv)
 	struct {
 		struct nlmsghdr			n;
 		__u32				flags;
-		char				ans[64];
 	} req = {
 		.n.nlmsg_len = NLMSG_LENGTH(sizeof(req.flags)),
 		.n.nlmsg_flags = NLM_F_REQUEST,
 		.n.nlmsg_type = XFRM_MSG_GETSADINFO,
 		.flags = 0XFFFFFFFF,
 	};
+	struct nlmsghdr *answer;
 
 	if (rtnl_open_byproto(&rth, 0, NETLINK_XFRM) < 0)
 		exit(1);
 
-	if (rtnl_talk(&rth, &req.n, &req.n, sizeof(req)) < 0)
+	if (rtnl_talk(&rth, &req.n, &answer) < 0)
 		exit(2);
 
-	print_sadinfo(&req.n, (void *)stdout);
+	print_sadinfo(answer, (void *)stdout);
 
+	free(answer);
 	rtnl_close(&rth);
 
 	return 0;
@@ -1376,7 +1378,7 @@ static int xfrm_state_flush(int argc, char **argv)
 		fprintf(stderr, "Flush state with XFRM-PROTO value \"%s\"\n",
 			strxf_xfrmproto(req.xsf.proto));
 
-	if (rtnl_talk(&rth, &req.n, NULL, 0) < 0)
+	if (rtnl_talk(&rth, &req.n, NULL) < 0)
 		exit(2);
 
 	rtnl_close(&rth);
diff --git a/lib/libgenl.c b/lib/libgenl.c
index 50d2d921..bb5fbb5f 100644
--- a/lib/libgenl.c
+++ b/lib/libgenl.c
@@ -49,16 +49,21 @@ int genl_resolve_family(struct rtnl_handle *grth, const char *family)
 {
 	GENL_REQUEST(req, 1024, GENL_ID_CTRL, 0, 0, CTRL_CMD_GETFAMILY,
 		     NLM_F_REQUEST);
+	struct nlmsghdr *answer;
+	int fnum;
 
 	addattr_l(&req.n, sizeof(req), CTRL_ATTR_FAMILY_NAME,
 		  family, strlen(family) + 1);
 
-	if (rtnl_talk(grth, &req.n, &req.n, sizeof(req)) < 0) {
+	if (rtnl_talk(grth, &req.n, &answer) < 0) {
 		fprintf(stderr, "Error talking to the kernel\n");
 		return -2;
 	}
 
-	return genl_parse_getfamily(&req.n);
+	fnum = genl_parse_getfamily(answer);
+	free(answer);
+
+	return fnum;
 }
 
 int genl_init_handle(struct rtnl_handle *grth, const char *family,
diff --git a/lib/libnetlink.c b/lib/libnetlink.c
index 1847c0be..4618dc0e 100644
--- a/lib/libnetlink.c
+++ b/lib/libnetlink.c
@@ -577,7 +577,7 @@ static void rtnl_talk_error(struct nlmsghdr *h, struct nlmsgerr *err,
 }
 
 static int __rtnl_talk(struct rtnl_handle *rtnl, struct nlmsghdr *n,
-		       struct nlmsghdr *answer, size_t maxlen,
+		       struct nlmsghdr **answer,
 		       bool show_rtnl_err, nl_ext_ack_fn_t errfn)
 {
 	int status;
@@ -651,9 +651,9 @@ static int __rtnl_talk(struct rtnl_handle *rtnl, struct nlmsghdr *n,
 					fprintf(stderr, "ERROR truncated\n");
 				} else if (!err->error) {
 					if (answer)
-						memcpy(answer, h,
-						       MIN(maxlen, h->nlmsg_len));
-					free(buf);
+						*answer = (struct nlmsghdr *)buf;
+					else
+						free(buf);
 					return 0;
 				}
 
@@ -667,9 +667,7 @@ static int __rtnl_talk(struct rtnl_handle *rtnl, struct nlmsghdr *n,
 			}
 
 			if (answer) {
-				memcpy(answer, h,
-				       MIN(maxlen, h->nlmsg_len));
-				free(buf);
+				*answer = (struct nlmsghdr *)buf;
 				return 0;
 			}
 
@@ -693,22 +691,22 @@ static int __rtnl_talk(struct rtnl_handle *rtnl, struct nlmsghdr *n,
 }
 
 int rtnl_talk(struct rtnl_handle *rtnl, struct nlmsghdr *n,
-	      struct nlmsghdr *answer, size_t maxlen)
+	      struct nlmsghdr **answer)
 {
-	return __rtnl_talk(rtnl, n, answer, maxlen, true, NULL);
+	return __rtnl_talk(rtnl, n, answer, true, NULL);
 }
 
 int rtnl_talk_extack(struct rtnl_handle *rtnl, struct nlmsghdr *n,
-		     struct nlmsghdr *answer, size_t maxlen,
+		     struct nlmsghdr **answer,
 		     nl_ext_ack_fn_t errfn)
 {
-	return __rtnl_talk(rtnl, n, answer, maxlen, true, errfn);
+	return __rtnl_talk(rtnl, n, answer, true, errfn);
 }
 
 int rtnl_talk_suppress_rtnl_errmsg(struct rtnl_handle *rtnl, struct nlmsghdr *n,
-				   struct nlmsghdr *answer, size_t maxlen)
+				   struct nlmsghdr **answer)
 {
-	return __rtnl_talk(rtnl, n, answer, maxlen, false, NULL);
+	return __rtnl_talk(rtnl, n, answer, false, NULL);
 }
 
 int rtnl_listen_all_nsid(struct rtnl_handle *rth)
diff --git a/misc/ss.c b/misc/ss.c
index 6b8eee6b..23710045 100644
--- a/misc/ss.c
+++ b/misc/ss.c
@@ -2696,7 +2696,7 @@ static int kill_inet_sock(struct nlmsghdr *h, void *arg, struct sockstat *s)
 		raw->sdiag_raw_protocol = s->raw_prot;
 	}
 
-	return rtnl_talk(rth, &req.nlh, NULL, 0);
+	return rtnl_talk(rth, &req.nlh, NULL);
 }
 
 static int show_one_inet_sock(const struct sockaddr_nl *addr,
diff --git a/tc/m_action.c b/tc/m_action.c
index 402228bb..8cbf7641 100644
--- a/tc/m_action.c
+++ b/tc/m_action.c
@@ -518,18 +518,18 @@ static int tc_action_gd(int cmd, unsigned int flags, int *argc_p, char ***argv_p
 	tail->rta_len = (void *) NLMSG_TAIL(&req.n) - (void *) tail;
 
 	req.n.nlmsg_seq = rth.dump = ++rth.seq;
-	if (cmd == RTM_GETACTION)
-		ans = &req.n;
 
-	if (rtnl_talk(&rth, &req.n, ans, MAX_MSG) < 0) {
+	if (rtnl_talk(&rth, &req.n, &ans) < 0) {
 		fprintf(stderr, "We have an error talking to the kernel\n");
 		return 1;
 	}
 
-	if (ans && print_action(NULL, &req.n, (void *)stdout) < 0) {
+	if (cmd == RTM_GETACTION && print_action(NULL, ans, stdout) < 0) {
 		fprintf(stderr, "Dump terminated\n");
+		free(ans);
 		return 1;
 	}
+	free(ans);
 
 	*argc_p = argc;
 	*argv_p = argv;
@@ -562,7 +562,7 @@ static int tc_action_modify(int cmd, unsigned int flags, int *argc_p, char ***ar
 	}
 	tail->rta_len = (void *) NLMSG_TAIL(&req.n) - (void *) tail;
 
-	if (rtnl_talk(&rth, &req.n, NULL, 0) < 0) {
+	if (rtnl_talk(&rth, &req.n, NULL) < 0) {
 		fprintf(stderr, "We have an error talking to the kernel\n");
 		ret = -1;
 	}
@@ -653,7 +653,7 @@ static int tc_act_list_or_flush(int *argc_p, char ***argv_p, int event)
 		req.n.nlmsg_type = RTM_DELACTION;
 		req.n.nlmsg_flags |= NLM_F_ROOT;
 		req.n.nlmsg_flags |= NLM_F_REQUEST;
-		if (rtnl_talk(&rth, &req.n, NULL, 0) < 0) {
+		if (rtnl_talk(&rth, &req.n, NULL) < 0) {
 			fprintf(stderr, "We have an error flushing\n");
 			return 1;
 		}
diff --git a/tc/tc_class.c b/tc/tc_class.c
index 1a1f1fa2..0214775b 100644
--- a/tc/tc_class.c
+++ b/tc/tc_class.c
@@ -149,7 +149,7 @@ static int tc_class_modify(int cmd, unsigned int flags, int argc, char **argv)
 		}
 	}
 
-	if (rtnl_talk(&rth, &req.n, NULL, 0) < 0)
+	if (rtnl_talk(&rth, &req.n, NULL) < 0)
 		return 2;
 
 	return 0;
diff --git a/tc/tc_filter.c b/tc/tc_filter.c
index cf290ae8..8dbebf1f 100644
--- a/tc/tc_filter.c
+++ b/tc/tc_filter.c
@@ -194,7 +194,7 @@ static int tc_filter_modify(int cmd, unsigned int flags, int argc, char **argv)
 		}
 	}
 
-	if (rtnl_talk(&rth, &req.n, NULL, 0) < 0) {
+	if (rtnl_talk(&rth, &req.n, NULL) < 0) {
 		fprintf(stderr, "We have an error talking to the kernel\n");
 		return 2;
 	}
@@ -331,6 +331,7 @@ static int tc_filter_get(int cmd, unsigned int flags, int argc, char **argv)
 		.t.tcm_parent = TC_H_UNSPEC,
 		.t.tcm_family = AF_UNSPEC,
 	};
+	struct nlmsghdr *answer;
 	struct filter_util *q = NULL;
 	__u32 prio = 0;
 	__u32 protocol = 0;
@@ -484,13 +485,14 @@ static int tc_filter_get(int cmd, unsigned int flags, int argc, char **argv)
 		return -1;
 	}
 
-	if (rtnl_talk(&rth, &req.n, &req.n, MAX_MSG) < 0) {
+	if (rtnl_talk(&rth, &req.n, &answer) < 0) {
 		fprintf(stderr, "We have an error talking to the kernel\n");
 		return 2;
 	}
 
-	print_filter(NULL, &req.n, (void *)stdout);
+	print_filter(NULL, answer, (void *)stdout);
 
+	free(answer);
 	return 0;
 }
 
diff --git a/tc/tc_qdisc.c b/tc/tc_qdisc.c
index 1e9d9097..c52114a2 100644
--- a/tc/tc_qdisc.c
+++ b/tc/tc_qdisc.c
@@ -190,7 +190,7 @@ static int tc_qdisc_modify(int cmd, unsigned int flags, int argc, char **argv)
 		req.t.tcm_ifindex = idx;
 	}
 
-	if (rtnl_talk(&rth, &req.n, NULL, 0) < 0)
+	if (rtnl_talk(&rth, &req.n, NULL) < 0)
 		return 2;
 
 	return 0;