From 1d5bafdfb2ca9d357ee3099baf4cce5e92f89527 Mon Sep 17 00:00:00 2001
From: Guus Sliepen <guus@sliepen.org>
Date: Sun, 19 Apr 2020 16:24:20 +0200
Subject: [PATCH] Add a callback that is triggered when the retransmission
 timeout expires.

This can be used by the application to detect potential network problems.
---
 utcp.c      | 8 ++++++++
 utcp.h      | 2 ++
 utcp_priv.h | 1 +
 3 files changed, 11 insertions(+)

diff --git a/utcp.c b/utcp.c
index 19f6cfa..20d86c2 100644
--- a/utcp.c
+++ b/utcp.c
@@ -890,6 +890,10 @@ static void retransmit(struct utcp_connection *c) {
 
 	struct utcp *utcp = c->utcp;
 
+	if (utcp->retransmit) {
+		utcp->retransmit(c);
+	}
+
 	struct {
 		struct hdr hdr;
 		uint8_t data[];
@@ -2447,6 +2451,10 @@ void utcp_offline(struct utcp *utcp, bool offline) {
 	}
 }
 
+void utcp_set_retransmit_cb(struct utcp *utcp, utcp_retransmit_t retransmit) {
+	utcp->retransmit = retransmit;
+}
+
 void utcp_set_clock_granularity(long granularity) {
 	CLOCK_GRANULARITY = granularity;
 }
diff --git a/utcp.h b/utcp.h
index aed177c..ff509ac 100644
--- a/utcp.h
+++ b/utcp.h
@@ -56,6 +56,7 @@ struct utcp_connection;
 
 typedef bool (*utcp_pre_accept_t)(struct utcp *utcp, uint16_t port);
 typedef void (*utcp_accept_t)(struct utcp_connection *utcp_connection, uint16_t port);
+typedef void (*utcp_retransmit_t)(struct utcp_connection *connection);
 
 typedef ssize_t (*utcp_send_t)(struct utcp *utcp, const void *data, size_t len);
 typedef ssize_t (*utcp_recv_t)(struct utcp_connection *connection, const void *data, size_t len);
@@ -92,6 +93,7 @@ extern void utcp_set_mtu(struct utcp *utcp, uint16_t mtu);
 extern void utcp_reset_timers(struct utcp *utcp);
 
 extern void utcp_offline(struct utcp *utcp, bool offline);
+extern void utcp_set_retransmit_cb(struct utcp *utcp, utcp_retransmit_t retransmit);
 
 // Per-socket options
 
diff --git a/utcp_priv.h b/utcp_priv.h
index 58e2715..197fd26 100644
--- a/utcp_priv.h
+++ b/utcp_priv.h
@@ -178,6 +178,7 @@ struct utcp {
 
 	utcp_accept_t accept;
 	utcp_pre_accept_t pre_accept;
+	utcp_retransmit_t retransmit;
 	utcp_send_t send;
 
 	// Packet buffer
-- 
2.39.2