Doc: Add hint about spamd and half-closed connections

[user/henk/code/exim.git] / doc / doc-docbook / spec.xfpt

diff --git a/doc/doc-docbook/spec.xfpt b/doc/doc-docbook/spec.xfpt
index f9a80558e01a14722b49af09c3f228b1c36535c7..c3fc1fb2145204e14f89aa04253276aa15980710 100644 (file)
--- a/doc/doc-docbook/spec.xfpt
+++ b/doc/doc-docbook/spec.xfpt
@@ -5044,7 +5044,7 @@ They can be used to conditionally include parts of a configuration
 The following classes of macros are defined:
 .display
 &` _HAVE_                     `&  build-time defines
-&` _DRVR_AUTH_                `&  authehticator drivers
+&` _DRVR_AUTH_                `&  authenticator drivers
 &` _DRVR_RTR_                 `&  router drivers
 &` _DRVR_TPT_                 `&  transport drivers
 &` _OPT_                      `&  configuration option support
@@ -31668,6 +31668,15 @@ configuration as follows (example):
 .code
 spamd_address = 192.168.99.45 387
 .endd
+The SpamAssassin protocol relies on a TCP half-close from the client.
+If your SpamAssassin client side is running a Linux system with an
+iptables firewall, consider setting
+&%net.netfilter.nf_conntrack_tcp_timeout_close_wait%& to at least the
+timeout, Exim uses when waiting for a response from the SpamAssassin
+server (currently defaulting to 120s).  With a lower value the Linux
+connection tracking may consider your half-closed connection as dead too
+soon.
+
 
 To use Rspamd (which by default listens on all local addresses
 on TCP port 11333)