From 304e94bc6ff67b6e9a71263aebba00eb1be32858 Mon Sep 17 00:00:00 2001
From: Nick Peng <pymumu@gmail.com>
Date: Sun, 19 Apr 2020 09:43:47 +0800
Subject: [PATCH] fast-ping: force send RST after ping finish.

---
 src/fast_ping.c |  5 +++++
 src/util.c      | 14 ++++++++++++++
 src/util.h      |  2 ++
 3 files changed, 21 insertions(+)

diff --git a/src/fast_ping.c b/src/fast_ping.c
index 1bdf67f..413c3c9 100644
--- a/src/fast_ping.c
+++ b/src/fast_ping.c
@@ -573,6 +573,11 @@ static int _fast_ping_sendping_tcp(struct ping_host_struct *ping_host)
 	setsockopt(fd, IPPROTO_TCP, TCP_NODELAY, &yes, sizeof(yes));
 	setsockopt(fd, SOL_SOCKET, SO_PRIORITY, &priority, sizeof(priority));
 	setsockopt(fd, IPPROTO_IP, IP_TOS, &ip_tos, sizeof(ip_tos));
+	set_sock_keepalive(fd, 0, 0, 0);
+	/* Set the socket lingering so we will RST connections instead of wasting
+	 * bandwidth with the four-step close
+	 */
+	set_sock_lingertime(fd, 0);
 
 	ping_host->seq++;
 	if (connect(fd, (struct sockaddr *)&ping_host->addr, ping_host->addr_len) != 0) {
diff --git a/src/util.c b/src/util.c
index a7f5983..8d0c39a 100644
--- a/src/util.c
+++ b/src/util.c
@@ -969,5 +969,19 @@ int set_sock_keepalive(int fd, int keepidle, int keepinterval, int keepcnt)
 	setsockopt(fd, IPPROTO_TCP, TCP_KEEPIDLE, &keepinterval, sizeof(keepinterval));
 	setsockopt(fd, IPPROTO_TCP, TCP_KEEPIDLE, &keepcnt, sizeof(keepcnt));
 
+	return 0;
+}
+
+int set_sock_lingertime(int fd, int time)
+{
+	struct linger l;
+
+	l.l_onoff = 1;
+	l.l_linger = 0;
+
+	if (setsockopt(fd, SOL_SOCKET, SO_LINGER, (const char *)&l, sizeof(l)) != 0) {
+		return -1;
+	}
+
 	return 0;
 }
\ No newline at end of file
diff --git a/src/util.h b/src/util.h
index b5c4390..1c581ae 100644
--- a/src/util.h
+++ b/src/util.h
@@ -102,6 +102,8 @@ int has_network_raw_cap(void);
 
 int set_sock_keepalive(int fd, int keepidle, int keepinterval, int keepcnt);
 
+int set_sock_lingertime(int fd, int time);
+
 #ifdef __cplusplus
 }
 #endif /*__cplusplus */