DOC: clarify how to make use of abstract sockets in socat

Socat's abstract sockets can be made compatible with haproxy's provided
that an option is passed. It's not obvious, so let's mention it in the
doc.

diff --git a/doc/configuration.txt b/doc/configuration.txt
index aa0062885f3d2e2f7cfd8c38a1ba34eca1709f9a..a4276f569f6d770a66fd1480acc2f3df4b0b7798 100644 (file)
--- a/doc/configuration.txt
+++ b/doc/configuration.txt
@@ -2190,6 +2190,12 @@ bind /<path> [, ...] [param*]
         listen external_bind_app1
             bind "fd@${FD_APP1}"
 
+  Note: regarding Linux's abstract namespace sockets, HAProxy uses the whole
+        sun_path length is used for the address length. Some other programs
+        such as socat use the string length only by default. Pass the option
+        ",unix-tightsocklen=0" to any abstract socket definition in socat to
+        make it compatible with HAProxy's.
+
   See also : "source", "option forwardfor", "unix-bind" and the PROXY protocol
              documentation, and section 5 about bind options.
 
@@ -6988,6 +6994,12 @@ server <name> <address>[:[port]] [param*]
         server www1_dc1 "${LAN_DC1}.101:80"
         server www1_dc2 "${LAN_DC2}.101:80"
 
+  Note: regarding Linux's abstract namespace sockets, HAProxy uses the whole
+        sun_path length is used for the address length. Some other programs
+        such as socat use the string length only by default. Pass the option
+        ",unix-tightsocklen=0" to any abstract socket definition in socat to
+        make it compatible with HAProxy's.
+
   See also: "default-server", "http-send-name-header" and section 5 about
              server options