>From 7c0d22d187400cf2445044f6526814a72b45a86d Mon Sep 17 00:00:00 2001
From: "F. Jason Park" <jp@neverwas.me>
Date: Wed, 8 Mar 2023 06:14:36 -0800
Subject: [PATCH] Add conditional erc-server-reconnect-function

* lisp/erc/erc-backend.el (erc--server-reconnect-timer,
erc-server-delayed-check-reconnect): Add possible alternate value for
option `erc-server-reconnect-function' that only attempts to reconnect
after hearing back from the server.  Also add helper variable.
---
 lisp/erc/erc-backend.el | 41 +++++++++++++++++++++++++++++++++++++++++
 1 file changed, 41 insertions(+)

diff --git a/lisp/erc/erc-backend.el b/lisp/erc/erc-backend.el
index 567443f5329..d1738e4f92d 100644
--- a/lisp/erc/erc-backend.el
+++ b/lisp/erc/erc-backend.el
@@ -744,6 +744,47 @@ erc-server-delayed-reconnect
     (with-current-buffer buffer
       (erc-server-reconnect))))
 
+(defvar-local erc--server-reconnect-timeout nil)
+
+(defun erc-server-delayed-check-reconnect (buffer)
+  "Wait for internet connectivity before trying to reconnect.
+BUFFER is the server buffer for the current connection."
+  (with-current-buffer buffer
+    (setq erc--server-reconnect-timeout
+          (min 300 (* (or erc--server-reconnect-timeout
+                          erc-server-reconnect-timeout)
+                      2)))
+    (let ((reschedule
+           (lambda (proc)
+             (let ((erc-server-reconnect-timeout
+                    erc--server-reconnect-timeout))
+               (with-current-buffer buffer
+                 (delete-process proc)
+                 (erc-display-message nil 'error buffer "Nobody home...")
+                 (erc-schedule-reconnect buffer 0))))))
+      (condition-case _
+          (make-network-process
+           :name "*erc-connectivity-check"
+           :host erc-session-server
+           :service erc-session-port
+           :nowait t
+           :filter
+           (lambda (proc _)
+             (delete-process proc)
+             (with-current-buffer buffer
+               (setq erc--server-reconnect-timeout nil))
+             (run-at-time nil nil #'erc-server-delayed-reconnect buffer))
+           :sentinel
+           (lambda (cproc event)
+             (with-current-buffer buffer
+               (pcase event
+                 ("open\n"
+                  (run-at-time nil nil #'send-string
+                               cproc "PING *connect-check*\r\n"))
+                 ("connection broken by remote peer\n"
+                  (funcall reschedule cproc))))))
+        (file-error (funcall reschedule nil))))))
+
 (defun erc-server-filter-function (process string)
   "The process filter for the ERC server."
   (with-current-buffer (process-buffer process)
-- 
2.39.2