From a657724f442899ec1ce16c8cfe9e63e8e9d861ff Mon Sep 17 00:00:00 2001
From: Rusty Russell <rusty@rustcorp.com.au>
Date: Thu, 18 Apr 2024 13:25:44 +0930
Subject: [PATCH] ccan/io: extended errors API so caller can be told if we fail
 accept()

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
---
 ccan/io/io.c   | 13 ++++++++++++-
 ccan/io/io.h   | 11 +++++++++++
 ccan/io/poll.c |  8 +++++---
 3 files changed, 28 insertions(+), 4 deletions(-)

diff --git a/ccan/io/io.c b/ccan/io/io.c
index 12df06d8..3d00de04 100644
--- a/ccan/io/io.c
+++ b/ccan/io/io.c
@@ -15,6 +15,7 @@
 void *io_loop_return;
 
 struct io_plan io_conn_freed;
+static bool io_extended_errors;
 
 struct io_listener *io_new_listener_(const tal_t *ctx, int fd,
 				     struct io_plan *(*init)(struct io_conn *,
@@ -540,7 +541,7 @@ struct io_plan *io_sock_shutdown(struct io_conn *conn)
 	/* And leave unset .*/
 	return &conn->plan[IO_IN];
 }
-	
+
 bool io_flush_sync(struct io_conn *conn)
 {
 	struct io_plan *plan = &conn->plan[IO_OUT];
@@ -576,3 +577,13 @@ again:
 	io_fd_block(io_conn_fd(conn), false);
 	return ok;
 }
+
+void io_set_extended_errors(bool state)
+{
+	io_extended_errors = state;
+}
+
+bool io_get_extended_errors(void)
+{
+	return io_extended_errors;
+}
diff --git a/ccan/io/io.h b/ccan/io/io.h
index eeb5e36e..cc92be2c 100644
--- a/ccan/io/io.h
+++ b/ccan/io/io.h
@@ -113,6 +113,8 @@ void io_set_finish_(struct io_conn *conn,
  * (tal'ocated off @ctx) and pass that to init().  Note that if there is
  * an error on this file descriptor, it will be freed.
  *
+ * Note: if the accept fails (usually due to EMFILE), init() will be called
+ * wth
  * Returns NULL on error (and sets errno).
  *
  * Example:
@@ -823,4 +825,13 @@ int (*io_poll_override(int (*poll)(struct pollfd *fds, nfds_t nfds, int timeout)
  */
 const void *io_have_fd(int fd, bool *listener);
 
+/**
+ * io_set_extended_errors - enable callbacks for errors.
+ * @state: true or false.
+ *
+ * Defaults false for compatibility.  See io_new_conn for what this changes.
+ */
+void io_set_extended_errors(bool state);
+bool io_get_extended_errors(void);
+
 #endif /* CCAN_IO_H */
diff --git a/ccan/io/poll.c b/ccan/io/poll.c
index 634f83d2..7fe9e2c5 100644
--- a/ccan/io/poll.c
+++ b/ccan/io/poll.c
@@ -270,10 +270,12 @@ static void accept_conn(struct io_listener *l)
 {
 	int fd = accept(l->fd.fd, NULL, NULL);
 
-	/* FIXME: What to do here? */
-	if (fd < 0)
+	if (fd < 0) {
+		/* If they've enabled it, this is how we tell them */
+		if (io_get_extended_errors())
+			l->init(NULL, l->arg);
 		return;
-
+	}
 	io_new_conn(l->ctx, fd, l->init, l->arg);
 }
 
-- 
2.39.5