[PATCH net-next v3 0/7] netconsole: validate a target's IP address configuration

[PATCH net-next v3 0/7] netconsole: validate a target's IP address configuration

[Gustavo Luiz Duarte]

This series adds two validations to the target configuration when the
user tries to enable it: first whether remote_ip was set, and second
whether local_ip and remote_ip address families match. Refuse to enable
the target if any of those validations fail.

These validations are already done for the target passed on the
command-line, so this aligns dynamic targets with the command-line
behavior.

The first two patches replace the per-target 'ipv6' flag with a
per-address 'family' field, which makes it easier to detect these error
conditions. Patches 3 and 4 implement the actual validations.

Patches 5-7 are follow-ups from previous reviews: move inet_addr from
netpoll.h into netconsole.c, show an unset address as an empty string
rather than "0.0.0.0", document local_ip auto-selection.

Signed-off-by: Gustavo Luiz Duarte <gustavold@gmail.com>
---
Changes in v3:
- Document local_ip auto-selection
- Link to v2: https://patch.msgid.link/20260810-netcons_ipv6-v2-0-3d4fc987a90f@gmail.com

Changes in v2:
- Show empty string in configfs for an unset IP address
- Moved inet_addr definition from netpoll.h to netconsole.c
- Moved address checks out of rtnl_lock()
- Link to v1: https://patch.msgid.link/20260805-netcons_ipv6-v1-0-170a35b92da1@gmail.com

To: Breno Leitao <leitao@debian.org>
To: Andrew Lunn <andrew+netdev@lunn.ch>
To: "David S. Miller" <davem@davemloft.net>
To: Eric Dumazet <edumazet@google.com>
To: Jakub Kicinski <kuba@kernel.org>
To: Paolo Abeni <pabeni@redhat.com>
To: Simon Horman <horms@kernel.org>
To: Jonathan Corbet <corbet@lwn.net>
To: Shuah Khan <skhan@linuxfoundation.org>
Cc: netdev@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Cc: linux-doc@vger.kernel.org

---
Gustavo Luiz Duarte (7):
      netconsole: add an address family to struct inet_addr
      netconsole: use the address family instead of the ipv6 flag
      netconsole: reject enabling a target with no remote IP address
      netconsole: reject a target mixing IPv4 and IPv6 addresses
      netconsole: show empty string for an unset IP address
      netconsole: move struct inet_addr into netconsole.c
      docs: netconsole: document local_ip auto-selection

 Documentation/networking/netconsole.rst |   5 ++
 drivers/net/netconsole.c                | 132 ++++++++++++++++----------------
 include/linux/netpoll.h                 |   5 --
 3 files changed, 70 insertions(+), 72 deletions(-)
---
base-commit: 4f93b12cf7b25fbf8e73d222722805b049f0a6d3
change-id: 20260730-netcons_ipv6-565d55f55729

Best regards,
--  
Gustavo Luiz Duarte <gustavold@gmail.com>

[PATCH net-next v3 1/7] netconsole: add an address family to struct inet_addr

[Gustavo Luiz Duarte]

netconsole_target stores a single 'bool ipv6' to denote the target's
address family. This makes it hard to detect conditions like "no address
set" or ipv4/ipv6 mixup between local_ip and remote_ip.

Add a 'family' field to inet_addr so each address stores its own address
family: AF_UNSPEC while unset, else AF_INET or AF_INET6.

Nothing reads the new field yet. The next patch switches the users over
and removes the bool. No functional change.

Reviewed-by: Breno Leitao <leitao@debian.org>
Signed-off-by: Gustavo Luiz Duarte <gustavold@gmail.com>
---
 drivers/net/netconsole.c | 24 +++++++++++++++---------
 include/linux/netpoll.h  | 10 +++++++---
 2 files changed, 22 insertions(+), 12 deletions(-)

diff --git a/drivers/net/netconsole.c b/drivers/net/netconsole.c
index b358e5c36735..432b66cf111a 100644
--- a/drivers/net/netconsole.c
+++ b/drivers/net/netconsole.c
@@ -225,7 +225,7 @@ struct netconsole_target {
 	bool			extended;
 	bool			release;
 	struct netpoll		np;
-	union inet_addr		local_ip, remote_ip;
+	struct inet_addr	local_ip, remote_ip;
 	bool			ipv6;
 	u16			local_port, remote_port;
 	u8			remote_mac[ETH_ALEN];
@@ -428,6 +428,7 @@ static int netcons_take_ipv6(struct netconsole_target *nt,
 				continue;
 			/* Got the IP, let's return */
 			nt->local_ip.in6 = ifp->addr;
+			nt->local_ip.family = AF_INET6;
 			err = 0;
 			break;
 		}
@@ -469,6 +470,7 @@ static int netcons_take_ipv4(struct netconsole_target *nt,
 	}
 
 	nt->local_ip.ip = ifa->ifa_local;
+	nt->local_ip.family = AF_INET;
 	np_info(np, "local IP %pI4\n", &nt->local_ip.ip);
 
 	return 0;
@@ -741,10 +743,10 @@ static void netconsole_print_banner(struct netconsole_target *nt)
 	np_info(np, "remote ethernet address %pM\n", nt->remote_mac);
 }
 
-/* Parse the string and populate the `inet_addr` union. Return 0 if IPv4 is
+/* Parse the string and populate the `inet_addr` struct. Return 0 if IPv4 is
  * populated, 1 if IPv6 is populated, and -1 upon failure.
  */
-static int netpoll_parse_ip_addr(const char *str, union inet_addr *addr)
+static int netpoll_parse_ip_addr(const char *str, struct inet_addr *addr)
 {
 	const char *end = NULL;
 	int len;
@@ -756,14 +758,18 @@ static int netpoll_parse_ip_addr(const char *str, union inet_addr *addr)
 	if (str[len - 1] == '\n')
 		len -= 1;
 
-	if (in4_pton(str, len, (void *)addr, -1, &end) > 0 &&
-	    (!end || *end == 0 || *end == '\n'))
+	if (in4_pton(str, len, (void *)&addr->ip, -1, &end) > 0 &&
+	    (!end || *end == 0 || *end == '\n')) {
+		addr->family = AF_INET;
 		return 0;
+	}
 
 	if (IS_ENABLED(CONFIG_IPV6) &&
-	    in6_pton(str, len, (void *)addr, -1, &end) > 0 &&
-	    (!end || *end == 0 || *end == '\n'))
+	    in6_pton(str, len, (void *)&addr->in6, -1, &end) > 0 &&
+	    (!end || *end == 0 || *end == '\n')) {
+		addr->family = AF_INET6;
 		return 1;
+	}
 
 	return -1;
 }
@@ -871,7 +877,7 @@ static ssize_t local_ip_show(struct config_item *item, char *buf)
 	if (nt->ipv6)
 		return sysfs_emit(buf, "%pI6c\n", &nt->local_ip.in6);
 	else
-		return sysfs_emit(buf, "%pI4\n", &nt->local_ip);
+		return sysfs_emit(buf, "%pI4\n", &nt->local_ip.ip);
 }
 
 static ssize_t remote_ip_show(struct config_item *item, char *buf)
@@ -881,7 +887,7 @@ static ssize_t remote_ip_show(struct config_item *item, char *buf)
 	if (nt->ipv6)
 		return sysfs_emit(buf, "%pI6c\n", &nt->remote_ip.in6);
 	else
-		return sysfs_emit(buf, "%pI4\n", &nt->remote_ip);
+		return sysfs_emit(buf, "%pI4\n", &nt->remote_ip.ip);
 }
 
 static ssize_t local_mac_show(struct config_item *item, char *buf)
diff --git a/include/linux/netpoll.h b/include/linux/netpoll.h
index 1c6b1eec5efd..de97f001a0f9 100644
--- a/include/linux/netpoll.h
+++ b/include/linux/netpoll.h
@@ -16,9 +16,13 @@
 #include <linux/ip.h>
 #include <linux/udp.h>
 
-union inet_addr {
-	__be32		ip;
-	struct in6_addr	in6;
+struct inet_addr {
+	/* Address family: AF_UNSPEC when unset, else AF_INET or AF_INET6 */
+	u8			family;
+	union {
+		__be32		ip;
+		struct in6_addr	in6;
+	};
 };
 
 struct netpoll {

-- 
2.55.0

[PATCH net-next v3 2/7] netconsole: use the address family instead of the ipv6 flag

[Gustavo Luiz Duarte]

Now that we have the address family in inet_addr, use that and remove
nt->ipv6.

We no longer need netcons_local_ip_unset() to check that all bytes are
zeroes, as that is now denoted by (family == AF_UNSPEC).

Reviewed-by: Breno Leitao <leitao@debian.org>
Signed-off-by: Gustavo Luiz Duarte <gustavold@gmail.com>
---
 drivers/net/netconsole.c | 82 ++++++++++++++----------------------------------
 1 file changed, 23 insertions(+), 59 deletions(-)

diff --git a/drivers/net/netconsole.c b/drivers/net/netconsole.c
index 432b66cf111a..351754d53cf9 100644
--- a/drivers/net/netconsole.c
+++ b/drivers/net/netconsole.c
@@ -195,7 +195,6 @@ struct netcons_userdata {
  *		local_mac	(read-only)
  * @local_ip:	Source IP address of the target (read-write).
  * @remote_ip:	Destination IP address of the target (read-write).
- * @ipv6:	Whether the target addresses are IPv6 (read-write).
  * @local_port:	Source UDP port of the target (read-write).
  * @remote_port: Destination UDP port of the target (read-write).
  * @remote_mac:	Destination ethernet address of the target (read-write).
@@ -226,7 +225,6 @@ struct netconsole_target {
 	bool			release;
 	struct netpoll		np;
 	struct inet_addr	local_ip, remote_ip;
-	bool			ipv6;
 	u16			local_port, remote_port;
 	u8			remote_mac[ETH_ALEN];
 	/* protected by target_list_lock; +1 gives scnprintf() room for its
@@ -476,23 +474,6 @@ static int netcons_take_ipv4(struct netconsole_target *nt,
 	return 0;
 }
 
-/*
- * Test whether the caller left nt->local_ip unset, so that
- * netcons_netpoll_setup() should auto-populate it from the egress device.
- *
- * nt->local_ip is a union of __be32 (IPv4) and struct in6_addr (IPv6),
- * so an IPv6 address whose first 4 bytes are zero (e.g. ::1, ::2,
- * IPv4-mapped ::ffff:a.b.c.d) must not be tested via the IPv4 arm —
- * doing so would misclassify a caller-supplied address as unset and
- * silently overwrite it with whatever address the device exposes.
- */
-static bool netcons_local_ip_unset(const struct netconsole_target *nt)
-{
-	if (nt->ipv6)
-		return ipv6_addr_any(&nt->local_ip.in6);
-	return !nt->local_ip.ip;
-}
-
 static int netcons_netpoll_setup(struct netconsole_target *nt)
 {
 	struct net *net = current->nsproxy->net_ns;
@@ -538,16 +519,13 @@ static int netcons_netpoll_setup(struct netconsole_target *nt)
 		rtnl_lock();
 	}
 
-	if (netcons_local_ip_unset(nt)) {
-		if (!nt->ipv6) {
-			err = netcons_take_ipv4(nt, ndev);
-			if (err)
-				goto put;
-		} else {
+	if (nt->local_ip.family == AF_UNSPEC) {
+		if (nt->remote_ip.family == AF_INET6)
 			err = netcons_take_ipv6(nt, ndev);
-			if (err)
-				goto put;
-		}
+		else
+			err = netcons_take_ipv4(nt, ndev);
+		if (err)
+			goto put;
 		ip_overwritten = true;
 	}
 
@@ -729,22 +707,22 @@ static void netconsole_print_banner(struct netconsole_target *nt)
 	struct netpoll *np = &nt->np;
 
 	np_info(np, "local port %d\n", nt->local_port);
-	if (nt->ipv6)
+	if (nt->local_ip.family == AF_INET6)
 		np_info(np, "local IPv6 address %pI6c\n", &nt->local_ip.in6);
 	else
 		np_info(np, "local IPv4 address %pI4\n", &nt->local_ip.ip);
 	np_info(np, "interface name '%s'\n", np->dev_name);
 	np_info(np, "local ethernet address '%pM'\n", np->dev_mac);
 	np_info(np, "remote port %d\n", nt->remote_port);
-	if (nt->ipv6)
+	if (nt->remote_ip.family == AF_INET6)
 		np_info(np, "remote IPv6 address %pI6c\n", &nt->remote_ip.in6);
 	else
 		np_info(np, "remote IPv4 address %pI4\n", &nt->remote_ip.ip);
 	np_info(np, "remote ethernet address %pM\n", nt->remote_mac);
 }
 
-/* Parse the string and populate the `inet_addr` struct. Return 0 if IPv4 is
- * populated, 1 if IPv6 is populated, and -1 upon failure.
+/* Parse the string and populate the `inet_addr` struct. Return 0 on success
+ * and -1 upon failure.
  */
 static int netpoll_parse_ip_addr(const char *str, struct inet_addr *addr)
 {
@@ -768,7 +746,7 @@ static int netpoll_parse_ip_addr(const char *str, struct inet_addr *addr)
 	    in6_pton(str, len, (void *)&addr->in6, -1, &end) > 0 &&
 	    (!end || *end == 0 || *end == '\n')) {
 		addr->family = AF_INET6;
-		return 1;
+		return 0;
 	}
 
 	return -1;
@@ -874,7 +852,7 @@ static ssize_t local_ip_show(struct config_item *item, char *buf)
 {
 	struct netconsole_target *nt = to_target(item);
 
-	if (nt->ipv6)
+	if (nt->local_ip.family == AF_INET6)
 		return sysfs_emit(buf, "%pI6c\n", &nt->local_ip.in6);
 	else
 		return sysfs_emit(buf, "%pI4\n", &nt->local_ip.ip);
@@ -884,7 +862,7 @@ static ssize_t remote_ip_show(struct config_item *item, char *buf)
 {
 	struct netconsole_target *nt = to_target(item);
 
-	if (nt->ipv6)
+	if (nt->remote_ip.family == AF_INET6)
 		return sysfs_emit(buf, "%pI6c\n", &nt->remote_ip.in6);
 	else
 		return sysfs_emit(buf, "%pI4\n", &nt->remote_ip.ip);
@@ -1232,7 +1210,6 @@ static ssize_t local_ip_store(struct config_item *item, const char *buf,
 {
 	struct netconsole_target *nt = to_target(item);
 	ssize_t ret = -EINVAL;
-	int ipv6;
 
 	dynamic_netconsole_mutex_lock();
 	if (nt->state == STATE_ENABLED) {
@@ -1241,10 +1218,8 @@ static ssize_t local_ip_store(struct config_item *item, const char *buf,
 		goto out_unlock;
 	}
 
-	ipv6 = netpoll_parse_ip_addr(buf, &nt->local_ip);
-	if (ipv6 == -1)
+	if (netpoll_parse_ip_addr(buf, &nt->local_ip) < 0)
 		goto out_unlock;
-	nt->ipv6 = !!ipv6;
 
 	ret = count;
 out_unlock:
@@ -1257,7 +1232,6 @@ static ssize_t remote_ip_store(struct config_item *item, const char *buf,
 {
 	struct netconsole_target *nt = to_target(item);
 	ssize_t ret = -EINVAL;
-	int ipv6;
 
 	dynamic_netconsole_mutex_lock();
 	if (nt->state == STATE_ENABLED) {
@@ -1266,10 +1240,8 @@ static ssize_t remote_ip_store(struct config_item *item, const char *buf,
 		goto out_unlock;
 	}
 
-	ipv6 = netpoll_parse_ip_addr(buf, &nt->remote_ip);
-	if (ipv6 == -1)
+	if (netpoll_parse_ip_addr(buf, &nt->remote_ip) < 0)
 		goto out_unlock;
-	nt->ipv6 = !!ipv6;
 
 	ret = count;
 out_unlock:
@@ -2078,7 +2050,7 @@ static void netpoll_udp_checksum(struct netconsole_target *nt,
 
 	/* check needs to be set, since it will be consumed in csum_partial */
 	udph->check = 0;
-	if (nt->ipv6)
+	if (nt->remote_ip.family == AF_INET6)
 		udph->check = csum_ipv6_magic(&nt->local_ip.in6,
 					      &nt->remote_ip.in6,
 					      udp_len, IPPROTO_UDP,
@@ -2119,7 +2091,7 @@ static void push_eth(struct netconsole_target *nt, struct sk_buff *skb)
 	skb_reset_mac_header(skb);
 	ether_addr_copy(eth->h_source, np->dev->dev_addr);
 	ether_addr_copy(eth->h_dest, nt->remote_mac);
-	if (nt->ipv6)
+	if (nt->remote_ip.family == AF_INET6)
 		eth->h_proto = htons(ETH_P_IPV6);
 	else
 		eth->h_proto = htons(ETH_P_IP);
@@ -2188,7 +2160,7 @@ static int netpoll_send_udp(struct netconsole_target *nt, const char *msg,
 		WARN_ON_ONCE(!irqs_disabled());
 
 	udp_len = len + sizeof(struct udphdr);
-	if (nt->ipv6)
+	if (nt->remote_ip.family == AF_INET6)
 		ip_len = udp_len + sizeof(struct ipv6hdr);
 	else
 		ip_len = udp_len + sizeof(struct iphdr);
@@ -2204,7 +2176,7 @@ static int netpoll_send_udp(struct netconsole_target *nt, const char *msg,
 	skb_put(skb, len);
 
 	push_udp(nt, skb, len);
-	if (nt->ipv6)
+	if (nt->remote_ip.family == AF_INET6)
 		push_ipv6(nt, skb, len);
 	else
 		push_ipv4(nt, skb, len);
@@ -2533,10 +2505,8 @@ __releases(&target_list_lock)
 static int netconsole_parser_cmdline(struct netconsole_target *nt, char *opt)
 {
 	struct netpoll *np = &nt->np;
-	bool ipversion_set = false;
 	char *cur = opt;
 	char *delim;
-	int ipv6;
 
 	if (*cur != '@') {
 		delim = strchr(cur, '@');
@@ -2550,16 +2520,12 @@ static int netconsole_parser_cmdline(struct netconsole_target *nt, char *opt)
 	cur++;
 
 	if (*cur != '/') {
-		ipversion_set = true;
 		delim = strchr(cur, '/');
 		if (!delim)
 			goto parse_failed;
 		*delim = 0;
-		ipv6 = netpoll_parse_ip_addr(cur, &nt->local_ip);
-		if (ipv6 < 0)
+		if (netpoll_parse_ip_addr(cur, &nt->local_ip) < 0)
 			goto parse_failed;
-		else
-			nt->ipv6 = (bool)ipv6;
 		cur = delim;
 	}
 	cur++;
@@ -2601,13 +2567,11 @@ static int netconsole_parser_cmdline(struct netconsole_target *nt, char *opt)
 	if (!delim)
 		goto parse_failed;
 	*delim = 0;
-	ipv6 = netpoll_parse_ip_addr(cur, &nt->remote_ip);
-	if (ipv6 < 0)
+	if (netpoll_parse_ip_addr(cur, &nt->remote_ip) < 0)
 		goto parse_failed;
-	else if (ipversion_set && nt->ipv6 != (bool)ipv6)
+	if (nt->local_ip.family != AF_UNSPEC &&
+	    nt->local_ip.family != nt->remote_ip.family)
 		goto parse_failed;
-	else
-		nt->ipv6 = (bool)ipv6;
 	cur = delim + 1;
 
 	if (*cur != 0) {

-- 
2.55.0

[PATCH net-next v3 3/7] netconsole: reject enabling a target with no remote IP address

[Gustavo Luiz Duarte]

The command-line path already requires a remote address, but if a user
creates a dynamic target and enables it without setting a remote
address, we currently try sending netconsole traffic to "0.0.0.0".

Refuse to enable a target if the remote address is unset.

Reviewed-by: Breno Leitao <leitao@debian.org>
Signed-off-by: Gustavo Luiz Duarte <gustavold@gmail.com>
---
 drivers/net/netconsole.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/net/netconsole.c b/drivers/net/netconsole.c
index 351754d53cf9..4af4f3039d4c 100644
--- a/drivers/net/netconsole.c
+++ b/drivers/net/netconsole.c
@@ -483,6 +483,11 @@ static int netcons_netpoll_setup(struct netconsole_target *nt)
 	bool ip_overwritten = false;
 	int err;
 
+	if (nt->remote_ip.family == AF_UNSPEC) {
+		np_err(np, "remote IP address not configured, aborting\n");
+		return -EDESTADDRREQ;
+	}
+
 	rtnl_lock();
 	if (np->dev_name[0])
 		ndev = __dev_get_by_name(net, np->dev_name);

-- 
2.55.0

[PATCH net-next v3 4/7] netconsole: reject a target mixing IPv4 and IPv6 addresses

[Gustavo Luiz Duarte]

The local_ip and remote_ip configfs attributes are written independently
and nothing stops a user from mixing ipv4 and ipv6. This leads to an
ipv4 address being zero-extended into an ipv6 header or an ipv6 address
being truncated to its first 4 bytes for an ipv4 header.

The command-line parser already refuses such a mismatch. This adds a
similar check when a dynamic target is being enabled.

Reviewed-by: Breno Leitao <leitao@debian.org>
Signed-off-by: Gustavo Luiz Duarte <gustavold@gmail.com>
---
 drivers/net/netconsole.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/net/netconsole.c b/drivers/net/netconsole.c
index 4af4f3039d4c..abcc8515ddd2 100644
--- a/drivers/net/netconsole.c
+++ b/drivers/net/netconsole.c
@@ -488,6 +488,12 @@ static int netcons_netpoll_setup(struct netconsole_target *nt)
 		return -EDESTADDRREQ;
 	}
 
+	if (nt->local_ip.family != AF_UNSPEC &&
+	    nt->local_ip.family != nt->remote_ip.family) {
+		np_err(np, "local and remote IP address families differ, aborting\n");
+		return -EINVAL;
+	}
+
 	rtnl_lock();
 	if (np->dev_name[0])
 		ndev = __dev_get_by_name(net, np->dev_name);

-- 
2.55.0

[PATCH net-next v3 5/7] netconsole: show empty string for an unset IP address

[Gustavo Luiz Duarte]

An unset address (local_ip/remote_ip), now denoted by AF_UNSPEC,
currently shows "0.0.0.0" in configfs. Print an empty string instead,
which is more clear.

In netconsole_print_banner() we can be even more explicit about it, as
we don't have the risk of userspace trying to parse it.

Reviewed-by: Breno Leitao <leitao@debian.org>
Signed-off-by: Gustavo Luiz Duarte <gustavold@gmail.com>
---
 drivers/net/netconsole.c | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/drivers/net/netconsole.c b/drivers/net/netconsole.c
index abcc8515ddd2..1f18d0a7d2dd 100644
--- a/drivers/net/netconsole.c
+++ b/drivers/net/netconsole.c
@@ -718,14 +718,18 @@ static void netconsole_print_banner(struct netconsole_target *nt)
 	struct netpoll *np = &nt->np;
 
 	np_info(np, "local port %d\n", nt->local_port);
-	if (nt->local_ip.family == AF_INET6)
+	if (nt->local_ip.family == AF_UNSPEC)
+		np_info(np, "local IP unset\n");
+	else if (nt->local_ip.family == AF_INET6)
 		np_info(np, "local IPv6 address %pI6c\n", &nt->local_ip.in6);
 	else
 		np_info(np, "local IPv4 address %pI4\n", &nt->local_ip.ip);
 	np_info(np, "interface name '%s'\n", np->dev_name);
 	np_info(np, "local ethernet address '%pM'\n", np->dev_mac);
 	np_info(np, "remote port %d\n", nt->remote_port);
-	if (nt->remote_ip.family == AF_INET6)
+	if (nt->remote_ip.family == AF_UNSPEC)
+		np_info(np, "remote IP unset\n");
+	else if (nt->remote_ip.family == AF_INET6)
 		np_info(np, "remote IPv6 address %pI6c\n", &nt->remote_ip.in6);
 	else
 		np_info(np, "remote IPv4 address %pI4\n", &nt->remote_ip.ip);
@@ -863,6 +867,8 @@ static ssize_t local_ip_show(struct config_item *item, char *buf)
 {
 	struct netconsole_target *nt = to_target(item);
 
+	if (nt->local_ip.family == AF_UNSPEC)
+		return sysfs_emit(buf, "\n");
 	if (nt->local_ip.family == AF_INET6)
 		return sysfs_emit(buf, "%pI6c\n", &nt->local_ip.in6);
 	else
@@ -873,6 +879,8 @@ static ssize_t remote_ip_show(struct config_item *item, char *buf)
 {
 	struct netconsole_target *nt = to_target(item);
 
+	if (nt->remote_ip.family == AF_UNSPEC)
+		return sysfs_emit(buf, "\n");
 	if (nt->remote_ip.family == AF_INET6)
 		return sysfs_emit(buf, "%pI6c\n", &nt->remote_ip.in6);
 	else

-- 
2.55.0

[PATCH net-next v3 6/7] netconsole: move struct inet_addr into netconsole.c

[Gustavo Luiz Duarte]

The struct inet_addr lives in netpoll.h, but since commit a1116396476f
("netconsole: move local_ip/remote_ip/ipv6 to netconsole_target") the
only user is netconsole. Move the definition into netconsole.c

Suggested-by: Breno Leitao <leitao@debian.org>
Reviewed-by: Breno Leitao <leitao@debian.org>
Signed-off-by: Gustavo Luiz Duarte <gustavold@gmail.com>
---
 drivers/net/netconsole.c | 9 +++++++++
 include/linux/netpoll.h  | 9 ---------
 2 files changed, 9 insertions(+), 9 deletions(-)

diff --git a/drivers/net/netconsole.c b/drivers/net/netconsole.c
index 1f18d0a7d2dd..267254f046de 100644
--- a/drivers/net/netconsole.c
+++ b/drivers/net/netconsole.c
@@ -151,6 +151,15 @@ enum target_state {
 	STATE_DEACTIVATED,
 };
 
+struct inet_addr {
+	/* Address family: AF_UNSPEC when unset, else AF_INET or AF_INET6 */
+	u8			family;
+	union {
+		__be32		ip;
+		struct in6_addr	in6;
+	};
+};
+
 /**
  * struct netcons_userdata - Formatted userdata payload of a target.
  * @rcu:	Used to free the payload after a grace period.
diff --git a/include/linux/netpoll.h b/include/linux/netpoll.h
index de97f001a0f9..ec0821a5b02d 100644
--- a/include/linux/netpoll.h
+++ b/include/linux/netpoll.h
@@ -16,15 +16,6 @@
 #include <linux/ip.h>
 #include <linux/udp.h>
 
-struct inet_addr {
-	/* Address family: AF_UNSPEC when unset, else AF_INET or AF_INET6 */
-	u8			family;
-	union {
-		__be32		ip;
-		struct in6_addr	in6;
-	};
-};
-
 struct netpoll {
 	struct net_device *dev;
 	netdevice_tracker dev_tracker;

-- 
2.55.0

[PATCH net-next v3 7/7] docs: netconsole: document local_ip auto-selection

[Gustavo Luiz Duarte]

An unset local_ip is auto-populated from the egress interface at enable
time, but any value the user writes, including 0.0.0.0, is used as-is.
This deviates from the behavior prior to "netconsole: use the address
family instead of the ipv6 flag", which interpreted 0.0.0.0 as unset.

Document this so the distinction between "unset" and "set to 0.0.0.0" is
clear.

Signed-off-by: Gustavo Luiz Duarte <gustavold@gmail.com>
---
 Documentation/networking/netconsole.rst | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/Documentation/networking/netconsole.rst b/Documentation/networking/netconsole.rst
index 4ab5d7b05cf1..694bca4803d5 100644
--- a/Documentation/networking/netconsole.rst
+++ b/Documentation/networking/netconsole.rst
@@ -141,6 +141,11 @@ The interface exposes these parameters of a netconsole target to userspace:
 	transmit_errors	Number of packet send errors		(read-only)
 	=============== =================================       ============
 
+local_ip is optional: if it is left unset, netconsole derives a source
+address from the egress interface when the target is enabled. Writing any
+value to it, including 0.0.0.0, uses that value verbatim and disables the
+automatic selection.
+
 The "enabled" attribute is also used to control whether the parameters of
 a target can be updated or not -- you can modify the parameters of only
 disabled targets (i.e. if "enabled" is 0).

-- 
2.55.0

Re: [PATCH net-next v3 7/7] docs: netconsole: document local_ip auto-selection

[Breno Leitao]

On Fri, Aug 14, 2026 at 08:28:58PM +0100, Gustavo Luiz Duarte wrote:
> An unset local_ip is auto-populated from the egress interface at enable
> time, but any value the user writes, including 0.0.0.0, is used as-is.
> This deviates from the behavior prior to "netconsole: use the address
> family instead of the ipv6 flag", which interpreted 0.0.0.0 as unset.
> 
> Document this so the distinction between "unset" and "set to 0.0.0.0" is
> clear.
> 
> Signed-off-by: Gustavo Luiz Duarte <gustavold@gmail.com>

Reviewed-by: Breno Leitao <leitao@debian.org>

Re: [PATCH net-next v3 0/7] netconsole: validate a target's IP address configuration

[Jakub Kicinski]

On Fri, 14 Aug 2026 20:28:51 +0100 Gustavo Luiz Duarte wrote:
> This series adds two validations to the target configuration when the
> user tries to enable it: first whether remote_ip was set, and second
> whether local_ip and remote_ip address families match. Refuse to enable
> the target if any of those validations fail.
> 
> These validations are already done for the target passed on the
> command-line, so this aligns dynamic targets with the command-line
> behavior.
> 
> The first two patches replace the per-target 'ipv6' flag with a
> per-address 'family' field, which makes it easier to detect these error
> conditions. Patches 3 and 4 implement the actual validations.
> 
> Patches 5-7 are follow-ups from previous reviews: move inet_addr from
> netpoll.h into netconsole.c, show an unset address as an empty string
> rather than "0.0.0.0", document local_ip auto-selection.

LGTM, but feels to risky to merge during the merge window.
Since we're changing semantics we should let this sit in linux-next
for at least a week. Please repost in Sept.

BTW please carefully review clashiko feedback:
https://netdev-ai.bots.linux.dev/sashiko/#/patchset/20260814-netcons_ipv6-v3-7-bc0915e8c75f@gmail.com
It marked as preexisting the problem of IP versions diverging but 
I think it's relevant (patch 2)?