Upstream: the "transparent" parameter of proxy_bind and friends.
This parameter lets binding the proxy connection to a non-local address.
Upstream will see the connection as coming from that address.
When used with $remote_addr, upstream will accept the connection from real
client address.
Example:
proxy_bind $remote_addr transparent;
diff --git a/auto/unix b/auto/unix
index 8c0e813..e6396ef 100755
--- a/auto/unix
+++ b/auto/unix
@@ -329,6 +329,44 @@
. auto/feature
+# NetBSD bind to any address for transparent proxying
+
+ngx_feature="SO_BINDANY"
+ngx_feature_name="NGX_HAVE_TRANSPARENT_PROXY"
+ngx_feature_run=no
+ngx_feature_incs="#include <sys/socket.h>"
+ngx_feature_path=
+ngx_feature_libs=
+ngx_feature_test="setsockopt(0, SOL_SOCKET, SO_BINDANY, NULL, 0)"
+. auto/feature
+
+
+# Linux transparent proxying
+
+ngx_feature="IP_TRANSPARENT"
+ngx_feature_name="NGX_HAVE_TRANSPARENT_PROXY"
+ngx_feature_run=no
+ngx_feature_incs="#include <sys/socket.h>
+ #include <netinet/in.h>"
+ngx_feature_path=
+ngx_feature_libs=
+ngx_feature_test="setsockopt(0, IPPROTO_IP, IP_TRANSPARENT, NULL, 0)"
+. auto/feature
+
+
+# FreeBSD bind to any address for transparent proxying
+
+ngx_feature="IP_BINDANY"
+ngx_feature_name="NGX_HAVE_TRANSPARENT_PROXY"
+ngx_feature_run=no
+ngx_feature_incs="#include <sys/socket.h>
+ #include <netinet/in.h>"
+ngx_feature_path=
+ngx_feature_libs=
+ngx_feature_test="setsockopt(0, IPPROTO_IP, IP_BINDANY, NULL, 0)"
+. auto/feature
+
+
# BSD way to get IPv4 datagram destination address
ngx_feature="IP_RECVDSTADDR"
