From 3674a436f68fb521aa4675c6fa7e1c8b3006854b Mon Sep 17 00:00:00 2001
From: Jeremie Leska <jeremie.leska@6wind.com>
Date: Fri, 22 May 2026 17:19:34 +0200
Subject: [PATCH] session server UPDATE allow binding on missing address

Add a cmake option to use IP_FREEBIND/IPV6_FREEBIND options.
Use the IP_FREEBIND/IPV6_FREEBIND on the socket to allow the bind even
if the address is not ready.

Signed-off-by: Jeremie Leska <jeremie.leska@6wind.com>
---
 CMakeLists.txt       |  6 ++++++
 src/config.h.in      |  3 +++
 src/session_server.c | 20 ++++++++++++++++++++
 3 files changed, 29 insertions(+)

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 42cb799e..ae347f2a 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -9,6 +9,7 @@ include(GNUInstallDirs)
 include(CheckFunctionExists)
 include(CheckCSourceCompiles)
 include(CheckIncludeFile)
+include(CheckSymbolExists)
 include(UseCompat)
 include(ABICheck)
 include(SourceFormat)
@@ -94,6 +95,7 @@ option(ENABLE_SSH_TLS "Enable NETCONF over SSH and TLS support (via libssh and O
 option(ENABLE_DNSSEC "Enable support for SSHFP retrieval using DNSSEC for SSH (requires OpenSSL and libval)" OFF)
 option(ENABLE_PAM "Detect and use PAM" ON)
 option(ENABLE_COMMON_TARGETS "Define common custom target names such as 'doc' or 'uninstall', may cause conflicts when using add_subdirectory() to build this project" ON)
+option(ENABLE_IP_FREEBIND "Enable the IP_FREEBIND/IPV6_FREEBIND options on the listening TCP socket" OFF)
 option(BUILD_SHARED_LIBS "By default, shared libs are enabled. Turn off for a static build." ON)
 set(READ_INACTIVE_TIMEOUT 20 CACHE STRING "Maximum number of seconds waiting for new data once some data have arrived")
 set(READ_ACTIVE_TIMEOUT 300 CACHE STRING "Maximum number of seconds for receiving a full message")
@@ -128,6 +130,10 @@ if(ENABLE_SSH_TLS)
     set(SSH_TLS_MACRO "#ifndef NC_ENABLED_SSH_TLS\n#define NC_ENABLED_SSH_TLS\n#endif")
 endif()
 
+if(ENABLE_IP_FREEBIND)
+    check_symbol_exists(IP_FREEBIND "netinet/in.h" NC_ENABLE_IP_FREEBIND)
+endif()
+
 set(headers
     src/log.h
     src/netconf.h
diff --git a/src/config.h.in b/src/config.h.in
index d366e0d9..3b2dc484 100644
--- a/src/config.h.in
+++ b/src/config.h.in
@@ -83,4 +83,7 @@
 /* Portability feature-check macros. */
 #cmakedefine HAVE_PTHREAD_RWLOCKATTR_SETKIND_NP
 
+/* Enable IP_FREEBIND/IPV6_FREEBIND on listening sockets. */
+#cmakedefine NC_ENABLE_IP_FREEBIND
+
 #endif /* NC_CONFIG_H_ */
diff --git a/src/session_server.c b/src/session_server.c
index c49a9012..b7c888af 100644
--- a/src/session_server.c
+++ b/src/session_server.c
@@ -289,6 +289,10 @@ nc_sock_bind_inet(int sock, const char *address, uint16_t port, int is_ipv4)
     struct sockaddr_in *saddr4;
     struct sockaddr_in6 *saddr6;
 
+#ifdef NC_ENABLE_IP_FREEBIND
+    int opt;
+#endif
+
     memset(&saddr, 0, sizeof(struct sockaddr_storage));
 
     if (is_ipv4) {
@@ -307,6 +311,14 @@ nc_sock_bind_inet(int sock, const char *address, uint16_t port, int is_ipv4)
             return -1;
         }
 
+#ifdef NC_ENABLE_IP_FREEBIND
+        opt = 1;
+        if (setsockopt(sock, IPPROTO_IP, IP_FREEBIND, &opt, sizeof(opt))) {
+            ERR(NULL, "Could not add IP_FREEBIND option (%s).", strerror(errno));
+            return -1;
+        }
+#endif
+
         if (bind(sock, (struct sockaddr *)saddr4, sizeof(struct sockaddr_in)) == -1) {
             ERR(NULL, "Could not bind %s:%" PRIu16 " (%s).", address, port, strerror(errno));
             return -1;
@@ -328,6 +340,14 @@ nc_sock_bind_inet(int sock, const char *address, uint16_t port, int is_ipv4)
             return -1;
         }
 
+#ifdef NC_ENABLE_IP_FREEBIND
+        opt = 1;
+        if (setsockopt(sock, IPPROTO_IPV6, IPV6_FREEBIND, &opt, sizeof(opt))) {
+            ERR(NULL, "Could not add IPV6_FREEBIND option (%s).", strerror(errno));
+            return -1;
+        }
+#endif
+
         if (bind(sock, (struct sockaddr *)saddr6, sizeof(struct sockaddr_in6)) == -1) {
             ERR(NULL, "Could not bind [%s]:%" PRIu16 " (%s).", address, port, strerror(errno));
             return -1;