From: Alexander Zubkov <green@qrator.net>
Date: Sat, 8 Jan 2022 17:31:56 +0000 (+0100)
Subject: IO: Support nonlocal bind in socket interface
X-Git-Tag: v2.0.9~19
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=87a02489f3880689a4e2ad72b0b981649dad2154;p=thirdparty%2Fbird.git

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 96fedeebb..0b6ac5898 100644
--- 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 c757960a1..f1887fb40 100644
--- 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 e21ff4874..f13eda7c0 100644
--- 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 3d67d0a7a..4fd774534 100644
--- 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");