mctpd: attempt a default configuration from /etc/mctpd.conf

Rather than requiring a -c FILE argument, allow a default configuration
file of /etc/mctpd.conf. We don't error if this is absent, to allow
running with the existing defaults.

Signed-off-by: Jeremy Kerr <[email protected]>

CHANGELOG.md

@@ -12,7 +12,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
 2. mctpd: Allow recovery of devices reporting a nil UUID for development
 3. mctpd: Allow configuring .Connectivity as writable for development
 4. mctpd: Add AssignEndpointStatic for static EID allocations
-5. mctpd: Add a configuration file facility
+5. mctpd: Add a configuration file facility, defaulting to /etc/mctpd.conf.
 
 ### Changed
 

README.md

@@ -68,8 +68,9 @@ configured (ie., interfaces are enabled, and local addresses have been
 assigned). There are two sample systemd unit files under the conf/ directory, to
 coordinate the local setup and the supervision of the mctpd process.
 
-`mctpd` can read some basic configuration from a file, if the `-c FILE` argument
-is given. An example configuration is in [`conf/mctpd.conf`](conf/mctpd.conf).
+`mctpd` can read some basic configuration from a file, by default
+`/etc/mctpd.conf`, but other files can be specified with the `-c FILE` argument.
+An example configuration is in [`conf/mctpd.conf`](conf/mctpd.conf).
 
 The `mctpd` daemon will expose a dbus interface, claiming the bus name
 `xyz.openbmc_project.MCTP` and object path `/xyz/openbmc_project/mctp`. This

meson.build

@@ -29,6 +29,11 @@ conf.set10('MCTPD_WRITABLE_CONNECTIVITY',
     get_option('unsafe-writable-connectivity'),
     description: 'Allow writes to the Connectivity member of the au.com.CodeConstruct.MCTP.Endpoint interface on endpoint objects')
 
+conf.set_quoted('MCTPD_CONF_FILE_DEFAULT',
+    join_paths(get_option('prefix'), get_option('sysconfdir'), 'mctpd.conf'),
+    description: 'Default configuration file path',
+)
+
 config_h = configure_file(
     output: 'config.h',
     configuration: conf,

src/mctpd.c

@@ -51,6 +51,8 @@
 // an arbitrary constant for use with sd_id128_get_machine_app_specific()
 static const char* mctpd_appid = "67369c05-4b97-4b7e-be72-65cfd8639f10";
 
+static const char *conf_file_default = MCTPD_CONF_FILE_DEFAULT;
+
 static mctp_eid_t eid_alloc_min = 0x08;
 static mctp_eid_t eid_alloc_max = 0xfe;
 
@@ -3654,25 +3656,32 @@ static int parse_config_mctp(ctx *ctx, toml_table_t *mctp_tab)
 static int parse_config(ctx *ctx)
 {
 	toml_table_t *conf_root, *mctp_tab;
+	bool conf_file_specified;
 	char errbuf[256] = { 0 };
+	const char *filename;
 	toml_datum_t val;
 	FILE *fp;
 	int rc;
 
-	if (!ctx->config_filename)
-		return 0;
+	conf_file_specified = !!ctx->config_filename;
+	filename = ctx->config_filename ?: conf_file_default;
 
 	rc = -1;
-	fp = fopen(ctx->config_filename, "r");
+	fp = fopen(filename, "r");
 	if (!fp) {
-		warn("can't open configuration file %s", ctx->config_filename);
-		return -1;
+		/* only fatal if a configuration file was specifed by args */
+		rc = 0;
+		if (conf_file_specified) {
+			warn("can't open configuration file %s", filename);
+			rc = -1;
+		}
+		return rc;
 	}
 
 	conf_root = toml_parse_file(fp, errbuf, sizeof(errbuf));
 	if (!conf_root) {
-		warnx("can't parse configuration file %s: %s",
-		      ctx->config_filename, errbuf);
+		warnx("can't parse configuration file %s: %s", filename,
+		      errbuf);
 		goto out_close;
 	}
 
@@ -3723,8 +3732,7 @@ int main(int argc, char **argv)
 
 	rc = parse_config(ctx);
 	if (rc) {
-		err(EXIT_FAILURE, "Can't load configuration file %s",
-		    ctx->config_filename);
+		err(EXIT_FAILURE, "Can't read configuration");
 	}
 
 	ctx->nl = mctp_nl_new(false);