[TESTS] add a simple program to test connection resets

The "reset" program may be used to send strings then reset connections.

tests/reset.c

@@ -0,0 +1,45 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+#include <netinet/in.h>
+#include <arpa/inet.h>
+#include <sys/types.h>
+#include <sys/socket.h>
+#include <fcntl.h>
+
+int main(int argc, char **argv) {
+	char *addr;
+	int port;
+	int sock;
+	struct sockaddr_in saddr;
+	const struct linger nolinger = { .l_onoff = 1, .l_linger = 0 };
+
+	if (argc < 4) {
+		fprintf(stderr,
+			"usage : %s <addr> <port> <string>\n"
+			"        This will connect to TCP port <addr>:<port> and send string <string>\n"
+			"        then immediately reset.\n",
+			argv[0]);
+		exit(1);
+	}
+
+	addr = argv[1];
+	port = atoi(argv[2]);
+
+	sock = socket(AF_INET, SOCK_STREAM, 0);
+	bzero(&saddr, sizeof(saddr));
+	saddr.sin_addr.s_addr = inet_addr(addr);
+	saddr.sin_port = htons(port);
+	saddr.sin_family = AF_INET;
+
+	if (connect(sock, (struct sockaddr *)&saddr, sizeof(saddr)) < 0) {
+		perror("connect");
+		exit(1);
+	}
+
+	send(sock, argv[3], strlen(argv[3]), MSG_DONTWAIT | MSG_NOSIGNAL);
+	setsockopt(sock, SOL_SOCKET, SO_LINGER, (struct linger *) &nolinger, sizeof(struct linger));
+	close(sock);
+	exit(0);
+}