From 0cbc33781e33602f35a677bc6a9688d3d8cf3031 Mon Sep 17 00:00:00 2001
From: Mikael Magnusson <mikma@users.sourceforge.net>
Date: Fri, 16 Oct 2020 23:42:24 +0200
Subject: add help option

---
 gre.c | 16 ++++++++++++++--
 1 file changed, 14 insertions(+), 2 deletions(-)

diff --git a/gre.c b/gre.c
index 68f4a14..b6d7cdb 100644
--- a/gre.c
+++ b/gre.c
@@ -62,6 +62,13 @@ static int daemonize(void);
 static int inet_addr_storage(const char *cp, struct sockaddr_storage *sp, size_t *sp_len);
 static int is_any(const struct sockaddr_storage *ss);
 
+static int usage(const char *arg0)
+{
+    printf("usage: %s [-n|--tun|-p|--tap] <tun> [remote] local\n", arg0);
+    exit(EXIT_FAILURE);
+}
+
+
 int main(int argc, char **argv)
 {
     fd_set readset;
@@ -71,6 +78,7 @@ int main(int argc, char **argv)
         int option_index = 0;
         static struct option long_options[] = {
             {"foreground", no_argument, 0, 'f' },
+            {"help", no_argument, 0, 'h' },
             {"tun", no_argument, 0,  'n' },
             {"tap", no_argument, 0,  'p' },
             {0,     0,           0,  0 }
@@ -85,6 +93,11 @@ int main(int argc, char **argv)
         case 'f':
             foreground = 1;
             break;
+
+        case 'h':
+            usage(argv[0]);
+            break;
+
         case 'n':
             printf("tun\n");
             type = IFF_TUN;
@@ -107,8 +120,7 @@ int main(int argc, char **argv)
 
     if (optnum < 2 || optnum  > 3)
     {
-        printf("usage: %s [-n|--tun|-p|--tap] <tun> [remote] local\n", argv[0]);
-        return EXIT_FAILURE;
+        usage(argv[0]);
     }
 
     const char *dev = argv[optind++];
-- 
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