Description: Shutdown and close sockets cleanly
 Cleanly shutdown and close sockets, this is supposed to allow for better
 TCP teardown on the remote end, and reduces CLOSE_WAIT time.
 .
 This patch was written 8 years ago, it is possible that nowadays nothing
 will benefit from a shutdown() right before close().  The commit log
 from eight years ago mentions that SHUT_RD should be upgraded to
 SHUT_RDWR where possible, but only after verification that this is not
 going to cause problems (e.g. by discarding data still on flight to the
 remote).
 .
 Also, it is possible that new daemons and utils in Cyrus 2.2 and 2.3 may
 need similar patches.
Author: Henrique de Moraes Holschuh <hmh@debian.org>
Forwarded: https://github.com/cyrusimap/cyrus-imapd/pull/3278
Reviewed-By: Xavier Guimard <yadd@debian.org
Last-Update: 2020-02-10

--- a/imap/fud.c
+++ b/imap/fud.c
@@ -147,6 +147,15 @@
     seen_done();
     closelog();
     cyrus_done();
+
+    /* be nice to remote */
+    shutdown(0, SHUT_RD);
+    shutdown(1, SHUT_RD);
+    shutdown(2, SHUT_RD);
+    close(0);
+    close(1);
+    close(2);
+
     exit(code);
 }
 
--- a/imap/imapd.c
+++ b/imap/imapd.c
@@ -1395,6 +1395,10 @@
 #ifdef HAVE_SSL
     tls_shutdown_serverengine();
 #endif
+    /* shutdown socket nicely */
+    cyrus_close_sock(0);
+    cyrus_close_sock(1);
+    cyrus_close_sock(2);
 
     saslprops_free(&saslprops);
 
--- a/imap/lmtpd.c
+++ b/imap/lmtpd.c
@@ -1119,6 +1119,9 @@
 
     cyrus_done();
 
+    /* shutdown socket nicely */
+    cyrus_reset_stdio();
+
     exit(code);
 }
 
--- a/imap/pop3d.c
+++ b/imap/pop3d.c
@@ -677,6 +677,9 @@
     saslprops_free(&saslprops);
 
     cyrus_done();
+    cyrus_close_sock(0);
+    cyrus_close_sock(1);
+    cyrus_close_sock(2);
 
     if (config_iolog) {
         read_io_count(io_count_stop);
