ns_enter() returns an integer... but it's always zero.  If we actually fail
the function doesn't return.  Therefore it makes more sense for this to be
a function returning void, and we can remove the cases where we pointlessly
checked its return value.

In addition ns_enter() is usually called from an ephemeral thread created
by NS_CALL().  That means that the exit(EXIT_FAILURE) there usually won't
be reported (since NS_CALL() doesn't wait() for the thread).  So, use die()
instead to print out some information in the unlikely event that our
setns() here does fail.

Signed-off-by: David Gibson <david(a)gibson.dropbear.id.au>
---
 conf.c | 3 ++-
 tap.c  | 4 ++--
 udp.c  | 6 ++----
 util.c | 8 +++-----
 util.h | 2 +-
 5 files changed, 10 insertions(+), 13 deletions(-)

diff --git a/conf.c b/conf.c
index 78eaf2d..a0622d2 100644
--- a/conf.c
+++ b/conf.c
@@ -101,9 +101,10 @@ static int get_bound_ports_ns(void *arg)
 	struct get_bound_ports_ns_arg *a = (struct get_bound_ports_ns_arg *)arg;
 	struct ctx *c = a->c;
 
-	if (!c->pasta_netns_fd || ns_enter(c))
+	if (!c->pasta_netns_fd)
 		return 0;
 
+	ns_enter(c);
 	get_bound_ports(c, 1, a->proto);
 
 	return 0;
diff --git a/tap.c b/tap.c
index a6a73d3..0f90cab 100644
--- a/tap.c
+++ b/tap.c
@@ -1182,9 +1182,9 @@ static int tap_ns_tun(void *arg)
 	struct ctx *c = (struct ctx *)arg;
 
 	memcpy(ifr.ifr_name, c->pasta_ifn, IFNAMSIZ);
+	ns_enter(c);
 
-	if (ns_enter(c) ||
-	    (tun_ns_fd = open("/dev/net/tun", flags)) < 0 ||
+	if ((tun_ns_fd = open("/dev/net/tun", flags)) < 0 ||
 	    ioctl(tun_ns_fd, TUNSETIFF, &ifr) ||
 	    !(c->pasta_ifi = if_nametoindex(c->pasta_ifn))) {
 		if (tun_ns_fd != -1)
diff --git a/udp.c b/udp.c
index 39c59d4..7be73f5 100644
--- a/udp.c
+++ b/udp.c
@@ -473,8 +473,7 @@ static int udp_splice_new_ns(void *arg)
 
 	a = (struct udp_splice_new_ns_arg *)arg;
 
-	if (ns_enter(a->c))
-		return 0;
+	ns_enter(a->c);
 
 	a->s = udp_splice_new(a->c, a->v6, a->src, true);
 
@@ -1068,8 +1067,7 @@ int udp_sock_init_ns(void *arg)
 	struct ctx *c = (struct ctx *)arg;
 	unsigned dst;
 
-	if (ns_enter(c))
-		return 0;
+	ns_enter(c);
 
 	for (dst = 0; dst < NUM_PORTS; dst++) {
 		if (!bitmap_isset(c->udp.fwd_out.f.map, dst))
diff --git a/util.c b/util.c
index 1d00404..2f9c27d 100644
--- a/util.c
+++ b/util.c
@@ -378,16 +378,14 @@ void procfs_scan_listen(struct ctx *c, uint8_t proto, int
ip_version, int ns,
  * ns_enter() - Enter configured user (unless already joined) and network ns
  * @c:		Execution context
  *
- * Return: 0, won't return on failure
+ * Won't return on failure
  *
  * #syscalls:pasta setns
  */
-int ns_enter(const struct ctx *c)
+void ns_enter(const struct ctx *c)
 {
 	if (setns(c->pasta_netns_fd, CLONE_NEWNET))
-		exit(EXIT_FAILURE);
-
-	return 0;
+		die("setns() failed entering netns: %s", strerror(errno));
 }
 
 /**
diff --git a/util.h b/util.h
index 26892aa..23dcad5 100644
--- a/util.h
+++ b/util.h
@@ -216,7 +216,7 @@ int bitmap_isset(const uint8_t *map, int bit);
 char *line_read(char *buf, size_t len, int fd);
 void procfs_scan_listen(struct ctx *c, uint8_t proto, int ip_version, int ns,
 			uint8_t *map, uint8_t *exclude);
-int ns_enter(const struct ctx *c);
+void ns_enter(const struct ctx *c);
 bool ns_is_init(void);
 void write_pidfile(int fd, pid_t pid);
 int __daemon(int pidfile_fd, int devnull_fd);
-- 
2.41.0

tap_ns_tun(), which runs in an ephemeral thread puts the fd it opens into
the global variable tun_ns_fd to communicate it back to the main thread
in tap_sock_tun_init().

However, the only thing tap_sock_tun_init() does with it is copies it to
c->fd_tap and everything else uses it from there.  tap_ns_tun() already
has access to the context structure, so we might as well store the value
directly in there rather than having a global as an intermediate.

Signed-off-by: David Gibson <david(a)gibson.dropbear.id.au>
---
 tap.c | 10 +++-------
 1 file changed, 3 insertions(+), 7 deletions(-)

diff --git a/tap.c b/tap.c
index a5d357a..e034f94 100644
--- a/tap.c
+++ b/tap.c
@@ -1165,8 +1165,6 @@ static void tap_sock_unix_new(struct ctx *c)
 	epoll_ctl(c->epollfd, EPOLL_CTL_ADD, c->fd_tap, &ev);
 }
 
-static int tun_ns_fd = -1;
-
 /**
  * tap_ns_tun() - Get tuntap fd in namespace
  * @c:		Execution context
@@ -1182,7 +1180,7 @@ static int tap_ns_tun(void *arg)
 	struct ctx *c = (struct ctx *)arg;
 	int fd, rc;
 
-	tun_ns_fd = -1;
+	c->fd_tap = -1;
 	memcpy(ifr.ifr_name, c->pasta_ifn, IFNAMSIZ);
 	ns_enter(c);
 
@@ -1197,7 +1195,7 @@ static int tap_ns_tun(void *arg)
 	if (!(c->pasta_ifi = if_nametoindex(c->pasta_ifn)))
 		die("Tap device opened but no network interface found");
 
-	tun_ns_fd = fd;
+	c->fd_tap = fd;
 
 	return 0;
 }
@@ -1211,13 +1209,11 @@ static void tap_sock_tun_init(struct ctx *c)
 	struct epoll_event ev = { 0 };
 
 	NS_CALL(tap_ns_tun, c);
-	if (tun_ns_fd == -1)
+	if (c->fd_tap == -1)
 		die("Failed to set up tap device in namespace");
 
 	pasta_ns_conf(c);
 
-	c->fd_tap = tun_ns_fd;
-
 	ev.data.fd = c->fd_tap;
 	ev.events = EPOLLIN | EPOLLRDHUP;
 	epoll_ctl(c->epollfd, EPOLL_CTL_ADD, c->fd_tap, &ev);
-- 
2.41.0