libbb: make bb_lookup_port() abort on bad port names

Also, no need to preserve errno

function                                             old     new   delta
.rodata                                           104247  104241      -6
bb_lookup_port                                        97      83     -14
nc_main                                             1039    1018     -21
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 0/3 up/down: 0/-41)             Total: -41 bytes

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

4 files changed, 10 insertions, 22 deletions

diff --git a/libbb/xconnect.c b/libbb/xconnect.c
index 5dd9cfd28..f1983a68b 100644
--- a/libbb/xconnect.c
+++ b/libbb/xconnect.c
@@ -115,27 +115,19 @@ void FAST_FUNC xconnect(int s, const struct sockaddr *s_addr, socklen_t addrlen)
 
 /* Return port number for a service.
  * If "port" is a number use it as the port.
- * If "port" is a name it is looked up in /etc/services,
- * if it isnt found return default_port
+ * If "port" is a name it is looked up in /etc/services.
+ * if NULL, return default_port
  */
-unsigned FAST_FUNC bb_lookup_port(const char *port, const char *protocol, unsigned default_port)
+unsigned FAST_FUNC bb_lookup_port(const char *port, const char *protocol, unsigned port_nr)
 {
-        unsigned port_nr = default_port;
         if (port) {
-                int old_errno;
-
-                /* Since this is a lib function, we're not allowed to reset errno to 0.
-                 * Doing so could break an app that is deferring checking of errno. */
-                old_errno = errno;
                 port_nr = bb_strtou(port, NULL, 10);
                 if (errno || port_nr > 65535) {
                         struct servent *tserv = getservbyname(port, protocol);
-                        port_nr = default_port;
-                        if (tserv)
-                                port_nr = ntohs(tserv->s_port);
-//FIXME: else: port string was garbage, but we don't report that???
+                        if (!tserv)
+                                bb_error_msg_and_die("bad port '%s'", port);
+                        port_nr = ntohs(tserv->s_port);
                 }
-                errno = old_errno;
         }
         return (uint16_t)port_nr;
 }
diff --git a/networking/ftpgetput.c b/networking/ftpgetput.c
index 30b3dabd1..4c92f34a1 100644
--- a/networking/ftpgetput.c
+++ b/networking/ftpgetput.c
@@ -290,8 +290,7 @@ static const char ftpgetput_longopts[] ALIGN1 =
 int ftpgetput_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
 int ftpgetput_main(int argc UNUSED_PARAM, char **argv)
 {
-        const char *port = "ftp";
-        /* socket to ftp server */
+        const char *port = NULL;
 
 #if ENABLE_FTPPUT && !ENABLE_FTPGET
 # define ftp_action ftp_send
diff --git a/networking/nc.c b/networking/nc.c
index 705b7356a..d351bf72a 100644
--- a/networking/nc.c
+++ b/networking/nc.c
@@ -216,7 +216,7 @@ int nc_main(int argc, char **argv)
                                 close(sfd);
                 } else {
                         cfd = create_and_connect_stream_or_die(argv[0],
-                                argv[1] ? bb_lookup_port(argv[1], "tcp", 0) : 0);
+                                bb_lookup_port(argv[1], "tcp", 0));
                 }
         }
 
diff --git a/networking/nc_bloaty.c b/networking/nc_bloaty.c
index 25b95246f..cfa133eae 100644
--- a/networking/nc_bloaty.c
+++ b/networking/nc_bloaty.c
@@ -813,8 +813,6 @@ int nc_main(int argc UNUSED_PARAM, char **argv)
         //if (option_mask32 & OPT_o) /* hexdump log */
         if (option_mask32 & OPT_p) { /* local source port */
                 o_lport = bb_lookup_port(str_p, o_udpmode ? "udp" : "tcp", 0);
-                if (!o_lport)
-                        bb_error_msg_and_die("bad local port '%s'", str_p);
         }
         //if (option_mask32 & OPT_r) /* randomize various things */
         //if (option_mask32 & OPT_u) /* use UDP */
@@ -827,9 +825,8 @@ int nc_main(int argc UNUSED_PARAM, char **argv)
 
         if (argv[0]) {
                 themaddr = xhost2sockaddr(argv[0],
-                        argv[1]
-                        ? bb_lookup_port(argv[1], o_udpmode ? "udp" : "tcp", 0)
-                        : 0);
+                        bb_lookup_port(argv[1], o_udpmode ? "udp" : "tcp", 0)
+                );
         }
 
         /* create & bind network socket */