better way to determine default port for SSH

1 files changed, 14 insertions, 2 deletions

diff --git a/src/cssh.c b/src/cssh.c
index bb03430..be138b4 100644
--- a/src/cssh.c
+++ b/src/cssh.c
@@ -13,6 +13,7 @@
 #include <pwd.h>
 #include <inttypes.h>
 #include <unistd.h>
+#include <netdb.h>
 
 #include "msleep.h"
 
@@ -20,6 +21,7 @@
 #include "version.h"
 
 #define BUFSIZE 4096
+#define DEFAULT_SSH_PORT 22
 
 typedef enum auth_state_e {
 	CSSH_AUTH_INIT,
@@ -161,6 +163,16 @@ ASK_AGAIN:
 	return true;
 }
 
+static unsigned short get_default_ssh_port( )
+{
+	struct servent *ent = getservbyname( "ssh", "tcp" );
+	if( ent != NULL ) {
+		return (unsigned short)ntohs( ent->s_port );
+	} else {
+		return DEFAULT_SSH_PORT;
+	}
+}
+
 static int accept_server( ssh_session session, unsigned char *hash, size_t hlen )
 {
 	char *hexa;
@@ -482,7 +494,7 @@ int main( int argc, char *argv[] )
 		case CSSH_EXECUTE_AS_SSH: {
 			// command line arguments are '[user@]host'
 			if( !args_info.hosts_file_given ) {
-				unsigned short default_port = 22;
+				unsigned short default_port = get_default_ssh_port( );
 				host = (char **)malloc( sizeof( char * ) );
 				port = (unsigned short *)malloc( sizeof( unsigned short ) );
 				if( args_info.inputs_num >= 1 ) {
@@ -541,7 +553,7 @@ int main( int argc, char *argv[] )
 		// for the hosts in the file containing hosts
 		
 		unsigned nof_hosts;
-		unsigned short default_port = 22;
+		unsigned short default_port = get_default_ssh_port( );
 		if( args_info.port_given ) {
 			default_port = args_info.port_arg;
 		}