mctpd: Add timeout overriding using program arguments

Currently, the timeout is hardcoded with the value of 250ms. However,
when developing, we may want to make the timeout longer to make sure we
do not miss any messages due to other reasons.

This commit adds timeout overriding using program arguments. This makes
tweaking the timeout at runtime possible.

Tested:

1. Send a request to a non-existent endpoint. It should timeout in 250ms
   by default.

       root@mtmitchell:~# time busctl call xyz.openbmc_project.MCTP /xyz/openbmc_project/mctp \
       > au.com.CodeConstruct.MCTP SetupEndpoint say mctppcie0 2 0xCA 0xFE
       Call failed: MCTP Endpoint did not respond

       real    0m0.344s
       user    0m0.016s
       sys     0m0.000s

2. Change mctpd.service to use longer timeout, 10 seconds for example.

       ExecStart=/usr/sbin/mctpd -t 10000000

3. Resend the request. It should timeout in 10 seconds.

       root@mtmitchell:~# time busctl call xyz.openbmc_project.MCTP /xyz/openbmc_project/mctp \
       > au.com.CodeConstruct.MCTP SetupEndpoint say mctppcie0 2 0xCA 0xFE
       Call failed: MCTP Endpoint did not respond

       real    0m10.083s
       user    0m0.015s
       sys     0m0.001s

Signed-off-by: Khang Nguyen <[email protected]>

Author: Khang Nguyen

src/mctpd.c

@@ -3074,9 +3074,10 @@ static int setup_testing(ctx *ctx) {
 
 static void print_usage(ctx *ctx)
 {
-	fprintf(stderr, "mctpd [-v] [-N]\n");
+	fprintf(stderr, "mctpd [-v] [-N] [-t usecs]\n");
 	fprintf(stderr, "      -v verbose\n");
 	fprintf(stderr, "      -N testing mode. Not safe for production\n");
+	fprintf(stderr, "      -t timeout in usecs\n");
 }
 
 static int parse_args(ctx *ctx, int argc, char **argv)
@@ -3085,12 +3086,16 @@ static int parse_args(ctx *ctx, int argc, char **argv)
 		{ .name = "help", .has_arg = no_argument, .val = 'h' },
 		{ .name = "verbose", .has_arg = no_argument, .val = 'v' },
 		{ .name = "testing", .has_arg = no_argument, .val = 'N' },
+		{ .name = "timeout", .has_arg = required_argument, .val = 't' },
 		{ 0 },
 	};
 	int c;
 
+	// default values
+	ctx->mctp_timeout = 250000; // 250ms
+
 	for (;;) {
-		c = getopt_long(argc, argv, "+hvN", options, NULL);
+		c = getopt_long(argc, argv, "+hvNt:", options, NULL);
 		if (c == -1)
 			break;
 
@@ -3101,6 +3106,13 @@ static int parse_args(ctx *ctx, int argc, char **argv)
 		case 'v':
 			ctx->verbose = true;
 			break;
+		case 't':
+			ctx->mctp_timeout = strtoull(optarg, NULL, 10);
+			if (ctx->mctp_timeout == 0) {
+				warnx("Timeout must be a non-zero u64");
+				return errno;
+			}
+			break;
 		case 'h':
 		default:
 			print_usage(ctx);
@@ -3138,7 +3150,6 @@ static int setup_config(ctx *ctx)
 {
 	int rc;
 	// TODO: this will go in a config file or arguments.
-	ctx->mctp_timeout = 250000; // 250ms
 	ctx->bus_owner = true;
 	rc = fill_uuid(ctx);
 	if (rc < 0)