IO: Support nonlocal bind in socket interface

Add option to socket interface for nonlocal binding, i.e. binding to an
IP address that is not present on interfaces. This behaviour is enabled
when SKF_FREEBIND socket flag is set. For Linux systems, it is
implemented by IP_FREEBIND socket flag.

Minor changes done by commiter.

diff --git a/lib/socket.h b/lib/socket.h
index 96fedeebbb26bdca11f6b44caac70cd38d32ad95..0b6ac5898d6d0db42bf393b8d06fb7e8f2fbc39b 100644 (file)
--- a/lib/socket.h
+++ b/lib/socket.h
@@ -123,6 +123,7 @@ extern int sk_priority_control;             /* Suggested priority for control traffic, shou
 #define SKF_TTL_RX     0x08    /* Report TTL / Hop Limit for RX packets */
 #define SKF_BIND       0x10    /* Bind datagram socket to given source address */
 #define SKF_HIGH_PORT  0x20    /* Choose port from high range if possible */
+#define SKF_FREEBIND   0x40    /* Allow socket to bind to a nonlocal address */
 
 #define SKF_THREAD     0x100   /* Socked used in thread, Do not add to main loop */
 #define SKF_TRUNCATED  0x200   /* Received packet was truncated, set by IO layer */

diff --git a/sysdep/bsd/sysio.h b/sysdep/bsd/sysio.h
index c757960a141149c6615a00c0cca97aea0c6f2607..f1887fb406b32fae44239274af325e45f5830c44 100644 (file)
--- a/sysdep/bsd/sysio.h
+++ b/sysdep/bsd/sysio.h
@@ -271,3 +271,9 @@ sk_set_priority(sock *s, int prio UNUSED)
 {
   ERR_MSG("Socket priority not supported");
 }
+
+static inline int
+sk_set_freebind(sock *s)
+{
+  ERR_MSG("Freebind is not supported");
+}

diff --git a/sysdep/linux/sysio.h b/sysdep/linux/sysio.h
index e21ff48743833308d3046fe48c470cff45499b25..f13eda7c08ad2b1f5b6847bd744d6656e478f4fb 100644 (file)
--- a/sysdep/linux/sysio.h
+++ b/sysdep/linux/sysio.h
@@ -10,6 +10,10 @@
 #define IPV6_MINHOPCOUNT 73
 #endif
 
+#ifndef IPV6_FREEBIND
+#define IPV6_FREEBIND 78
+#endif
+
 #ifndef TCP_MD5SIG_EXT
 #define TCP_MD5SIG_EXT 32
 #endif
@@ -266,3 +270,18 @@ sk_set_priority(sock *s, int prio)
   return 0;
 }
 
+static inline int
+sk_set_freebind(sock *s)
+{
+  int y = 1;
+
+  if (sk_is_ipv4(s))
+    if (setsockopt(s->fd, SOL_IP, IP_FREEBIND, &y, sizeof(y)) < 0)
+      ERR("IP_FREEBIND");
+
+  if (sk_is_ipv6(s))
+    if (setsockopt(s->fd, SOL_IPV6, IPV6_FREEBIND, &y, sizeof(y)) < 0)
+      ERR("IPV6_FREEBIND");
+
+  return 0;
+}

diff --git a/sysdep/unix/io.c b/sysdep/unix/io.c
index 3d67d0a7a8f07e6baf45d14470af3c5d897a05de..4fd774534f1f488ea600d4643cd1bd98d927e47f 100644 (file)
--- a/sysdep/unix/io.c
+++ b/sysdep/unix/io.c
@@ -1436,6 +1436,10 @@ sk_open(sock *s)
        if (sk_set_high_port(s) < 0)
          log(L_WARN "Socket error: %s%#m", s->err);
 
+    if (s->flags & SKF_FREEBIND)
+      if (sk_set_freebind(s) < 0)
+        log(L_WARN "Socket error: %s%#m", s->err);
+
     sockaddr_fill(&sa, s->af, bind_addr, s->iface, bind_port);
     if (bind(fd, &sa.sa, SA_LEN(sa)) < 0)
       ERR2("bind");