commit 1cf6c3b02bc9d72cb437805d7ca90250b52fcdee
Author: Matthieu Herrb <matthieu.herrb@laas.fr>
Date:   Sun Jul 15 09:54:00 2012 +0200

    Echoc: a simple udb based link monitoriing application.
    
    Uses the echo service on the other end to send back paquets.

diff --git a/Makefile b/Makefile
new file mode 100644
index 0000000..4f298eb
--- /dev/null
+++ b/Makefile
@@ -0,0 +1,14 @@
+#
+
+PROG= echoc
+SRCS= echoc.c
+
+OBJS= $(SRCS:%.c=%.o)
+
+all: $(PROG)
+
+$(PROG): $(OBJS)
+	$(CC) -o $@ $(OBJS)
+
+.c.o:
+	$(CC) -c $(CFLAGS) -o $@ $<
diff --git a/echoc.c b/echoc.c
new file mode 100644
index 0000000..ddc4ac9
--- /dev/null
+++ b/echoc.c
@@ -0,0 +1,156 @@
+/*
+ * Copyright (c) 2012 Matthieu Herrb <matthieu@herrb.eu>
+ *
+ * Permission to use, copy, modify, and distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+#include <sys/types.h>
+#include <sys/socket.h>
+#include <sys/time.h>
+
+#include <err.h>
+#include <errno.h>
+#include <netdb.h>
+#include <poll.h>
+#include <signal.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <time.h>
+#include <unistd.h>
+
+int sock = -1;
+int verbose = 0;
+struct sockaddr *server;
+socklen_t serverlen;
+unsigned int seq = 0;
+
+#define THRESHOLD 10 
+
+static void
+usage(void)
+{
+	errx(2, "usage: echoc [-v] server");
+}
+
+
+int
+main(int argc, char *argv[])
+{
+	char name[NI_MAXHOST];
+	struct sockaddr_storage client;
+	struct addrinfo hints, *res, *res0;
+	struct timeval tv;
+	struct pollfd pfd[1];
+	socklen_t addrlen;
+	int ch;
+	int nfds, received = 0;
+	int error, dropped, buffer, last;
+	extern int optind;
+
+	setbuf(stdout, NULL);
+	while ((ch = getopt(argc, argv, "v")) != -1) {
+		switch (ch) {
+		case 'v':
+			verbose = 1;
+			break;
+		default:
+			usage();
+		}
+	}
+	argc -= optind;
+	argv += optind;
+	if (argc != 1)
+		usage();
+
+	memset(&hints, 0, sizeof(hints));
+	hints.ai_family = PF_UNSPEC;
+	hints.ai_socktype = SOCK_DGRAM;
+	error = getaddrinfo(argv[0], "echo", &hints, &res0);
+	if (error)
+		errx(1, "%s", gai_strerror(error));
+
+	for (res = res0; res != NULL; res = res->ai_next) {
+		sock = socket(res->ai_family, res->ai_socktype,
+		    res->ai_protocol);
+		if (sock != -1) {
+			server = res->ai_addr;
+			serverlen = res->ai_addrlen;
+			break;
+		}
+	}
+	if (sock == -1)
+		err(1, "socket");
+
+	dropped = 0;
+	memset(&client, 0, sizeof(client));
+	gettimeofday(&tv, NULL);
+	while (1) {
+		if (sendto(sock, &seq, sizeof(seq), 0, server,
+			serverlen) != sizeof(seq)) {
+			if (verbose)
+				warn("sendto");
+		}
+		seq++;
+		
+		pfd[0].fd = sock;
+		pfd[0].events = POLLIN;
+		nfds = poll(pfd, 1, 200);
+		if (nfds == -1 && errno != EINTR)
+			warn("poll error");
+		if ((nfds == 0) || (nfds == -1 && errno == EINTR)) {
+			if (dropped == THRESHOLD) {
+				struct tm *tm = localtime((time_t *)&tv.tv_sec);
+				char buf[80];
+				strftime(buf, sizeof(buf), "%F %T", tm);
+				printf("%s.%06ld: lost connection\n", 
+				    buf, tv.tv_usec);
+			}
+			dropped++;
+			continue;
+		}
+
+		if ((received = recvfrom(sock, &buffer, sizeof(buffer),
+			    MSG_DONTWAIT,
+			    (struct sockaddr *) &client,
+			    &addrlen)) != sizeof(buffer)) {
+			warn("recvfrom");
+		}
+
+		if (verbose && (serverlen != addrlen ||
+			memcmp(&client, server, addrlen) != 0)) {
+			if ((error = getnameinfo((struct sockaddr *)&client,
+				addrlen, name, sizeof(name),
+				    NULL, 0, NI_DGRAM)) != 0) {
+				warnx("%s", gai_strerror(error));
+			} else {
+				warnx("received data from unknown host %s",
+				    name);
+			}
+		}
+		gettimeofday(&tv, NULL);
+		if (dropped >= THRESHOLD) {
+			struct tm *tm = localtime((time_t *)&tv.tv_sec);
+			char buf[80];
+			strftime(buf, sizeof(buf), "%F %T", tm);
+			printf("%s.%02ld: connection is back\n", 
+			    buf, tv.tv_usec);
+			dropped = 0;
+		}
+		last = buffer;
+		if (verbose)
+			printf("%d %ld.%06ld\n", buffer, tv.tv_sec, tv.tv_usec);
+		usleep(100000);
+	}
+	close(sock);
+	exit(0);
+}