Added -4 -6 Switches and default tcp46

As *BSD defaults to use IPv6 only sockets and Linux to IPv4 mapped IPv6 sockets, switches to support explicit binding address families are required. Now set explicitly if you want IPv6 only, IPv4 only or mapped IPv4. Caveat: OpenBSD explicitly states to not support IPv4 mapped IPv6 via setsock-API
2025-07-01 06:40:04 +02:00 · 2019-04-03 17:11:04 +02:00
parent cb7ee90cf5
commit badf3dd69e
3 changed files with 95 additions and 13 deletions
--- a/README.md
+++ b/README.md
@ -19,6 +19,8 @@ Usage information is printed with `-h`.

 ```
 Usage: endlessh [-vh] [-d MS] [-f CONFIG] [-l LEN] [-m LIMIT] [-p PORT]
+  -4        Bind to IPv4 only
+  -6        Bind to IPv6 only
  -d INT    Message millisecond delay [10000]
  -f        Set and load config file [/etc/endlessh/config]
  -h        Print this help message and exit
@ -69,6 +71,12 @@ MaxClients 4096
 #   1 = Standard, useful log messages
 #   2 = Very noisy debugging information
 LogLevel 0
+
+# Set the family of the listening socket
+#   0 = Use IPv4 Mapped IPv6 (Both v4 and v6, default)
+#   4 = Use IPv4 only
+#   6 = Use IPv6 only
+BindFamily 0
 ```

 ## Build issues
--- a/endlessh.c
+++ b/endlessh.c
@ -23,6 +23,7 @@
 #define DEFAULT_MAX_LINE_LENGTH     32
 #define DEFAULT_MAX_CLIENTS       4096
 #define DEFAULT_CONFIG_FILE      "/etc/endlessh/config"
+#define DEFAULT_BIND_FAMILY  AF_UNSPEC

 #define XSTR(s) STR(s)
 #define STR(s) #s
@ -87,6 +88,7 @@ client_new(int fd, long long send_next)
        c->bytes_sent = 0;
        c->next = 0;
        c->fd = fd;
+        c->port = 0;

        /* Set the smallest possible recieve buffer. This reduces local
         * resource usage and slows down the remote end.
@ -231,6 +233,7 @@ struct config {
    int delay;
    int max_line_length;
    int max_clients;
+    int bind_family;
 };

 #define CONFIG_DEFAULT { \
@ -238,6 +241,7 @@ struct config {
    .delay           = DEFAULT_DELAY, \
    .max_line_length = DEFAULT_MAX_LINE_LENGTH, \
    .max_clients     = DEFAULT_MAX_CLIENTS, \
+    .bind_family     = DEFAULT_BIND_FAMILY, \
 }

 static void
@ -300,6 +304,27 @@ config_set_max_line_length(struct config *c, const char *s, int hardfail)
    }
 }

+static void
+config_set_bind_family(struct config *c, const char *s, int hardfail)
+{
+  switch (*s) {
+      case '4':
+          c->bind_family = AF_INET;
+          break;
+      case '6':
+          c->bind_family = AF_INET6;
+          break;
+      case '0':
+          c->bind_family = AF_UNSPEC;
+          break;
+      default:
+          fprintf(stderr, "endlessh: Invalid address family: %s\n", s);
+          if (hardfail)
+              exit(EXIT_FAILURE);
+          break;
+  }
+}
+
 enum config_key {
    KEY_INVALID,
    KEY_PORT,
@ -307,6 +332,7 @@ enum config_key {
    KEY_MAX_LINE_LENGTH,
    KEY_MAX_CLIENTS,
    KEY_LOG_LEVEL,
+    KEY_BIND_FAMILY,
 };

 static enum config_key
@ -318,6 +344,7 @@ config_key_parse(const char *tok)
        [KEY_MAX_LINE_LENGTH] = "MaxLineLength",
        [KEY_MAX_CLIENTS]     = "MaxClients",
        [KEY_LOG_LEVEL]       = "LogLevel",
+        [KEY_BIND_FAMILY]     = "BindFamily"
    };
    for (size_t i = 1; i < sizeof(table) / sizeof(*table); i++)
        if (!strcmp(tok, table[i]))
@ -384,6 +411,9 @@ config_load(struct config *c, const char *file, int hardfail)
                case KEY_MAX_CLIENTS:
                    config_set_max_clients(c, tokens[1], hardfail);
                    break;
+                case KEY_BIND_FAMILY:
+                    config_set_bind_family(c, tokens[1], hardfail);
+                    break;
                case KEY_LOG_LEVEL: {
                    errno = 0;
                    char *end;
@ -410,13 +440,19 @@ config_log(const struct config *c)
    logmsg(LOG_INFO, "Delay %ld", c->delay);
    logmsg(LOG_INFO, "MaxLineLength %d", c->max_line_length);
    logmsg(LOG_INFO, "MaxClients %d", c->max_clients);
+    logmsg(LOG_INFO, "BindFamily %s",
+        c->bind_family == AF_INET6 ? "IPv6 Only" :
+        c->bind_family == AF_INET  ? "IPv4 Only" :
+                                "IPv4 Mapped IPv6");
 }

 static void
 usage(FILE *f)
 {
-    fprintf(f, "Usage: endlessh [-vh] [-d MS] [-f CONFIG] [-l LEN] "
+    fprintf(f, "Usage: endlessh [-vh] [-46] [-d MS] [-f CONFIG] [-l LEN] "
                               "[-m LIMIT] [-p PORT]\n");
+    fprintf(f, "  -4        Bind to IPv4 only");
+    fprintf(f, "  -6        Bind to IPv6 only");
    fprintf(f, "  -d INT    Message millisecond delay ["
            XSTR(DEFAULT_DELAY) "]\n");
    fprintf(f, "  -f        Set and load config file ["
@ -439,11 +475,11 @@ print_version(void)
 }

 static int
-server_create(int port)
+server_create(int port, int family)
 {
    int r, s, value;

-    s = socket(AF_INET6, SOCK_STREAM, 0);
+    s = socket(family == AF_UNSPEC ? AF_INET6 : family, SOCK_STREAM, 0);
    logmsg(LOG_DEBUG, "socket() = %d", s);
    if (s == -1) die();

@ -454,12 +490,37 @@ server_create(int port)
    if (r == -1)
        logmsg(LOG_DEBUG, "errno = %d, %s", errno, strerror(errno));

-    struct sockaddr_in6 addr = {
-        .sin6_family = AF_INET6,
-        .sin6_port = htons(port),
-        .sin6_addr = in6addr_any
-    };
-    r = bind(s, (void *)&addr, sizeof(addr));
+    /*
+     * With OpenBSD IPv6 sockets are always IPv6-only, so the socket option
+     * is read-only (not modifiable).
+     * http://man.openbsd.org/ip6#IPV6_V6ONLY
+     */
+#ifndef __OpenBSD__
+    if (family == AF_INET6 || family == AF_UNSPEC) {
+        errno = 0;
+        value = (family == AF_INET6);
+        r = setsockopt(s, IPPROTO_IPV6, IPV6_V6ONLY, &value, sizeof(value));
+        logmsg(LOG_DEBUG, "setsockopt(%d, IPV6_V6ONLY, true) = %d", s, r);
+        if (r == -1)
+            logmsg(LOG_DEBUG, "errno = %d, %s", errno, strerror(errno));
+    }
+#endif
+
+    if (family == AF_INET) {
+        struct sockaddr_in addr4 = {
+            .sin_family = AF_INET,
+            .sin_port = htons(port),
+            .sin_addr = {INADDR_ANY}
+        };
+        r = bind(s, (void *)&addr4, sizeof(addr4));
+    } else {
+        struct sockaddr_in6 addr6 = {
+            .sin6_family = AF_INET6,
+            .sin6_port = htons(port),
+            .sin6_addr = in6addr_any
+        };
+        r = bind(s, (void *)&addr6, sizeof(addr6));
+    }
    logmsg(LOG_DEBUG, "bind(%d, port=%d) = %d", s, port, r);
    if (r == -1) die();

@ -503,8 +564,14 @@ main(int argc, char **argv)
    config_load(&config, config_file, 1);

    int option;
-    while ((option = getopt(argc, argv, "d:f:hl:m:p:vV")) != -1) {
+    while ((option = getopt(argc, argv, "46d:f:hl:m:p:vV")) != -1) {
        switch (option) {
+            case '4':
+                config_set_bind_family(&config, "4", 1);
+                break;
+            case '6':
+                config_set_bind_family(&config, "6", 1);
+                break;
            case 'd':
                config_set_delay(&config, optarg, 1);
                break;
@ -567,17 +634,18 @@ main(int argc, char **argv)

    unsigned long rng = uepoch();

-    int server = server_create(config.port);
+    int server = server_create(config.port, config.bind_family);

    while (running) {
        if (reload) {
            /* Configuration reload requested (SIGHUP) */
            int oldport = config.port;
+            int oldfamily = config.bind_family;
            config_load(&config, config_file, 0);
            config_log(&config);
-            if (oldport != config.port) {
+            if (oldport != config.port || oldfamily != config.bind_family) {
                close(server);
-                server = server_create(config.port);
+                server = server_create(config.port, config.bind_family);
            }
            reload = 0;
        }
--- a/util/smf/endlessh.conf
+++ b/util/smf/endlessh.conf
@ -19,3 +19,9 @@ MaxClients 4096
 #   1 = Standard, useful log messages
 #   2 = Very noisy debugging information
 LogLevel 1
+
+# Set the family of the listening socket
+#   0 = Use IPv4 Mapped IPv6 (Both v4 and v6, default)
+#   4 = Use IPv4 only
+#   6 = Use IPv6 only
+BindFamily 0