[PATCH 2/9] conf: Move mode detection into helper function

[David Gibson <david@gibson.dropbear.id.au>]

One of the first things we need to do is determine if we're in passt mode
or pasta mode.  Currently this is open-coded in main(), by examining
argv[0].  We want to complexify this a bit in future to cover vhost-user
mode as well.  Prepare for this, by moving the mode detection into a new
conf_mode() function.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
---
 conf.c  | 26 ++++++++++++++++++++++++++
 conf.h  |  1 +
 passt.c | 14 ++------------
 3 files changed, 29 insertions(+), 12 deletions(-)

diff --git a/conf.c b/conf.c
index 7f20bc84..2022ea1d 100644
--- a/conf.c
+++ b/conf.c
@@ -991,6 +991,32 @@ pasta_opts:
 	_exit(status);
 }
 
+/**
+ * conf_mode() - Determine passt/pasta's operating mode from command line
+ * @argc:	Argument count
+ * @argv:	Command line arguments
+ *
+ * Return: mode to operate in, PASTA or PASST
+ */
+/* cppcheck-suppress constParameter */
+enum passt_modes conf_mode(int argc, char *argv[])
+{
+	char argv0[PATH_MAX], *basearg0;
+
+	if (argc < 1)
+		die("Cannot determine argv[0]");
+
+	strncpy(argv0, argv[0], PATH_MAX - 1);
+	basearg0 = basename(argv0);
+	if (strstr(basearg0, "pasta"))
+		return MODE_PASTA;
+
+	if (strstr(basearg0, "passt"))
+		return MODE_PASST;
+
+	die("Cannot determine mode, invoke as \"passt\" or \"pasta\"");
+}
+
 /**
  * conf_print() - Print fundamental configuration parameters
  * @c:		Execution context
diff --git a/conf.h b/conf.h
index 9d2143db..b45ad746 100644
--- a/conf.h
+++ b/conf.h
@@ -6,6 +6,7 @@
 #ifndef CONF_H
 #define CONF_H
 
+enum passt_modes conf_mode(int argc, char *argv[]);
 void conf(struct ctx *c, int argc, char **argv);
 
 #endif /* CONF_H */
diff --git a/passt.c b/passt.c
index 868842b0..0bd2a292 100644
--- a/passt.c
+++ b/passt.c
@@ -191,7 +191,6 @@ int main(int argc, char **argv)
 {
 	struct epoll_event events[EPOLL_EVENTS];
 	int nfds, i, devnull_fd = -1;
-	char argv0[PATH_MAX], *name;
 	struct ctx c = { 0 };
 	struct rlimit limit;
 	struct timespec now;
@@ -213,21 +212,12 @@ int main(int argc, char **argv)
 	sigaction(SIGTERM, &sa, NULL);
 	sigaction(SIGQUIT, &sa, NULL);
 
-	if (argc < 1)
-		_exit(EXIT_FAILURE);
+	c.mode = conf_mode(argc, argv);
 
-	strncpy(argv0, argv[0], PATH_MAX - 1);
-	name = basename(argv0);
-	if (strstr(name, "pasta")) {
+	if (c.mode == MODE_PASTA) {
 		sa.sa_handler = pasta_child_handler;
 		if (sigaction(SIGCHLD, &sa, NULL))
 			die_perror("Couldn't install signal handlers");
-
-		c.mode = MODE_PASTA;
-	} else if (strstr(name, "passt")) {
-		c.mode = MODE_PASST;
-	} else {
-		_exit(EXIT_FAILURE);
 	}
 
 	if (signal(SIGPIPE, SIG_IGN) == SIG_ERR)
-- 
@@ -191,7 +191,6 @@ int main(int argc, char **argv)
 {
 	struct epoll_event events[EPOLL_EVENTS];
 	int nfds, i, devnull_fd = -1;
-	char argv0[PATH_MAX], *name;
 	struct ctx c = { 0 };
 	struct rlimit limit;
 	struct timespec now;
@@ -213,21 +212,12 @@ int main(int argc, char **argv)
 	sigaction(SIGTERM, &sa, NULL);
 	sigaction(SIGQUIT, &sa, NULL);
 
-	if (argc < 1)
-		_exit(EXIT_FAILURE);
+	c.mode = conf_mode(argc, argv);
 
-	strncpy(argv0, argv[0], PATH_MAX - 1);
-	name = basename(argv0);
-	if (strstr(name, "pasta")) {
+	if (c.mode == MODE_PASTA) {
 		sa.sa_handler = pasta_child_handler;
 		if (sigaction(SIGCHLD, &sa, NULL))
 			die_perror("Couldn't install signal handlers");
-
-		c.mode = MODE_PASTA;
-	} else if (strstr(name, "passt")) {
-		c.mode = MODE_PASST;
-	} else {
-		_exit(EXIT_FAILURE);
 	}
 
 	if (signal(SIGPIPE, SIG_IGN) == SIG_ERR)
-- 
2.48.1