diff mbox series

[net-next,v6,2/2] netconsole: allow selection of egress interface via MAC address

Message ID 20250312-netconsole-v6-2-3437933e79b8@purestorage.com (mailing list archive)
State New
Delegated to: Netdev Maintainers
Headers show
Series netconsole: allow selection of egress interface via MAC address | expand

Checks

Context Check Description
netdev/series_format success Posting correctly formatted
netdev/tree_selection success Clearly marked for net-next
netdev/ynl success Generated files up to date; no warnings/errors; no diff in generated;
netdev/fixes_present success Fixes tag not required for -next series
netdev/header_inline success No static functions without inline keyword in header files
netdev/build_32bit success Errors and warnings before: 0 this patch: 0
netdev/build_tools success Errors and warnings before: 26 (+0) this patch: 26 (+0)
netdev/cc_maintainers success CCed 8 of 8 maintainers
netdev/build_clang success Errors and warnings before: 0 this patch: 0
netdev/verify_signedoff success Signed-off-by tag matches author and committer
netdev/deprecated_api success None detected
netdev/check_selftest success No net selftest shell script
netdev/verify_fixes success No Fixes tag
netdev/build_allmodconfig_warn success Errors and warnings before: 21 this patch: 21
netdev/checkpatch success total: 0 errors, 0 warnings, 0 checks, 142 lines checked
netdev/build_clang_rust success No Rust files in patch. Skipping build
netdev/kdoc success Errors and warnings before: 0 this patch: 0
netdev/source_inline success Was 0 now: 0
netdev/contest success net-next-2025-03-13--00-00 (tests: 894)

Commit Message

Uday Shankar March 12, 2025, 7:51 p.m. UTC 
Currently, netconsole has two methods of configuration - module
parameter and configfs. The former interface allows for netconsole
activation earlier during boot (by specifying the module parameter on
the kernel command line), so it is preferred for debugging issues which
arise before userspace is up/the configfs interface can be used. The
module parameter syntax requires specifying the egress interface name.
This requirement makes it hard to use for a couple reasons:
- The egress interface name can be hard or impossible to predict. For
  example, installing a new network card in a system can change the
  interface names assigned by the kernel.
- When constructing the module parameter, one may have trouble
  determining the original (kernel-assigned) name of the interface
  (which is the name that should be given to netconsole) if some stable
  interface naming scheme is in effect. A human can usually look at
  kernel logs to determine the original name, but this is very painful
  if automation is constructing the parameter.

For these reasons, allow selection of the egress interface via MAC
address when configuring netconsole using the module parameter. Update
the netconsole documentation with an example of the new syntax.
Selection of egress interface by MAC address via configfs is far less
interesting (since when this interface can be used, one should be able
to easily convert between MAC address and interface name), so it is left
unimplemented.

Signed-off-by: Uday Shankar <ushankar@purestorage.com>
Reviewed-by: Breno Leitao <leitao@debian.org>
Tested-by: Breno Leitao <leitao@debian.org>
Reviewed-by: Simon Horman <horms@kernel.org>
---
 Documentation/networking/netconsole.rst |  6 +++-
 include/linux/netpoll.h                 |  6 ++++
 net/core/netpoll.c                      | 51 +++++++++++++++++++++++++--------
 3 files changed, 50 insertions(+), 13 deletions(-)
diff mbox series

Patch

diff --git a/Documentation/networking/netconsole.rst b/Documentation/networking/netconsole.rst
index ae82a6337a8d8a07a0d691e2da170f6cf70ae86f..ec740ba127976bf9c978d7b2811fb1735c1a004e 100644
--- a/Documentation/networking/netconsole.rst
+++ b/Documentation/networking/netconsole.rst
@@ -47,7 +47,7 @@  following format::
 	r             if present, prepend kernel version (release) to the message
 	src-port      source for UDP packets (defaults to 6665)
 	src-ip        source IP to use (interface address)
-	dev           network interface (eth0)
+	dev           network interface name (eth0) or MAC address
 	tgt-port      port for logging agent (6666)
 	tgt-ip        IP address for logging agent
 	tgt-macaddr   ethernet MAC address for logging agent (broadcast)
@@ -64,6 +64,10 @@  or using IPv6::
 
  insmod netconsole netconsole=@/,@fd00:1:2:3::1/
 
+or using a MAC address to select the egress interface::
+
+   linux netconsole=4444@10.0.0.1/22:33:44:55:66:77,9353@10.0.0.2/12:34:56:78:9a:bc
+
 It also supports logging to multiple remote agents by specifying
 parameters for the multiple agents separated by semicolons and the
 complete string enclosed in "quotes", thusly::
diff --git a/include/linux/netpoll.h b/include/linux/netpoll.h
index f6e8abe0b1f19a34a35ec976c127be468d863028..0477208ed9ffa5cc57b072dce35f0789169fc37b 100644
--- a/include/linux/netpoll.h
+++ b/include/linux/netpoll.h
@@ -25,7 +25,13 @@  union inet_addr {
 struct netpoll {
 	struct net_device *dev;
 	netdevice_tracker dev_tracker;
+	/*
+	 * Either dev_name or dev_mac can be used to specify the local
+	 * interface - dev_name is used if it is a nonempty string, else
+	 * dev_mac is used.
+	 */
 	char dev_name[IFNAMSIZ];
+	u8 dev_mac[ETH_ALEN];
 	const char *name;
 
 	union inet_addr local_ip, remote_ip;
diff --git a/net/core/netpoll.c b/net/core/netpoll.c
index 8a0df2b274a88213f4ca4632ecbb66d74ac960a9..976202d10297a6d7687b8251561ae73c64118f57 100644
--- a/net/core/netpoll.c
+++ b/net/core/netpoll.c
@@ -502,7 +502,8 @@  void netpoll_print_options(struct netpoll *np)
 		np_info(np, "local IPv6 address %pI6c\n", &np->local_ip.in6);
 	else
 		np_info(np, "local IPv4 address %pI4\n", &np->local_ip.ip);
-	np_info(np, "interface '%s'\n", np->dev_name);
+	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", np->remote_port);
 	if (np->ipv6)
 		np_info(np, "remote IPv6 address %pI6c\n", &np->remote_ip.in6);
@@ -572,11 +573,18 @@  int netpoll_parse_options(struct netpoll *np, char *opt)
 	cur++;
 
 	if (*cur != ',') {
-		/* parse out dev name */
+		/* parse out dev_name or dev_mac */
 		if ((delim = strchr(cur, ',')) == NULL)
 			goto parse_failed;
 		*delim = 0;
-		strscpy(np->dev_name, cur, sizeof(np->dev_name));
+
+		np->dev_name[0] = '\0';
+		eth_broadcast_addr(np->dev_mac);
+		if (!strchr(cur, ':'))
+			strscpy(np->dev_name, cur, sizeof(np->dev_name));
+		else if (!mac_pton(cur, np->dev_mac))
+			goto parse_failed;
+
 		cur = delim;
 	}
 	cur++;
@@ -690,27 +698,45 @@  int __netpoll_setup(struct netpoll *np, struct net_device *ndev)
 }
 EXPORT_SYMBOL_GPL(__netpoll_setup);
 
+/*
+ * Returns a pointer to a string representation of the identifier used
+ * to select the egress interface for the given netpoll instance. buf
+ * must be a buffer of length at least MAC_ADDR_STR_LEN + 1.
+ */
+static char *egress_dev(struct netpoll *np, char *buf)
+{
+	if (np->dev_name[0])
+		return np->dev_name;
+
+	snprintf(buf, MAC_ADDR_STR_LEN, "%pM", np->dev_mac);
+	return buf;
+}
+
 int netpoll_setup(struct netpoll *np)
 {
+	struct net *net = current->nsproxy->net_ns;
+	char buf[MAC_ADDR_STR_LEN + 1];
 	struct net_device *ndev = NULL;
 	bool ip_overwritten = false;
 	struct in_device *in_dev;
 	int err;
 
 	rtnl_lock();
-	if (np->dev_name[0]) {
-		struct net *net = current->nsproxy->net_ns;
+	if (np->dev_name[0])
 		ndev = __dev_get_by_name(net, np->dev_name);
-	}
+	else if (is_valid_ether_addr(np->dev_mac))
+		ndev = dev_getbyhwaddr(net, ARPHRD_ETHER, np->dev_mac);
+
 	if (!ndev) {
-		np_err(np, "%s doesn't exist, aborting\n", np->dev_name);
+		np_err(np, "%s doesn't exist, aborting\n", egress_dev(np, buf));
 		err = -ENODEV;
 		goto unlock;
 	}
 	netdev_hold(ndev, &np->dev_tracker, GFP_KERNEL);
 
 	if (netdev_master_upper_dev_get(ndev)) {
-		np_err(np, "%s is a slave device, aborting\n", np->dev_name);
+		np_err(np, "%s is a slave device, aborting\n",
+		       egress_dev(np, buf));
 		err = -EBUSY;
 		goto put;
 	}
@@ -718,7 +744,8 @@  int netpoll_setup(struct netpoll *np)
 	if (!netif_running(ndev)) {
 		unsigned long atmost;
 
-		np_info(np, "device %s not up yet, forcing it\n", np->dev_name);
+		np_info(np, "device %s not up yet, forcing it\n",
+			egress_dev(np, buf));
 
 		err = dev_open(ndev, NULL);
 
@@ -752,7 +779,7 @@  int netpoll_setup(struct netpoll *np)
 			if (!ifa) {
 put_noaddr:
 				np_err(np, "no IP address for %s, aborting\n",
-				       np->dev_name);
+				       egress_dev(np, buf));
 				err = -EDESTADDRREQ;
 				goto put;
 			}
@@ -783,13 +810,13 @@  int netpoll_setup(struct netpoll *np)
 			}
 			if (err) {
 				np_err(np, "no IPv6 address for %s, aborting\n",
-				       np->dev_name);
+				       egress_dev(np, buf));
 				goto put;
 			} else
 				np_info(np, "local IPv6 %pI6c\n", &np->local_ip.in6);
 #else
 			np_err(np, "IPv6 is not supported %s, aborting\n",
-			       np->dev_name);
+			       egress_dev(np, buf));
 			err = -EINVAL;
 			goto put;
 #endif