From 60a751dc4220728692f441557e9cff977ee26ed1 Mon Sep 17 00:00:00 2001
From: sbwml <admin@cooluc.com>
Date: Mon, 4 Aug 2025 21:21:50 +0800
Subject: [PATCH] tcping: add IPv6 support

- Refactor connect_to to use getaddrinfo for dual-stack (IPv4/IPv6) support
- Remove gethostbyname usage in main.c, pass hostname as string
- tcping now works with both IPv4 and IPv6 addresses

Signed-off-by: sbwml <admin@cooluc.com>
---
 main.c | 20 ++++++++++------
 tcp.c  | 75 ++++++++++++++++++++++++++--------------------------------
 tcp.h  |  2 +-
 3 files changed, 48 insertions(+), 49 deletions(-)

--- a/main.c
+++ b/main.c
@@ -43,7 +43,6 @@ int main(int argc, char *argv[])
 	int wait = 1, quiet = 0;
 	int ok = 0, err = 0;
 	double min = 999999999999999.0, avg = 0.0, max = 0.0;
-	struct hostent  *hostdnsentries;
 
 		while((c = getopt(argc, argv, "p:c:i:t:fq?")) != -1)
 		{
@@ -87,12 +86,19 @@ int main(int argc, char *argv[])
 	}
 	hostname = argv[optind];
 
-	hostdnsentries = gethostbyname(hostname);
-	if (hostdnsentries == NULL)
-	{
-		fprintf(stderr, "%s: Name or service not known\n", hostname);
+	// domain name resolution
+	struct addrinfo hints, *res = NULL;
+	memset(&hints, 0, sizeof(hints));
+	hints.ai_family = AF_UNSPEC;
+	hints.ai_socktype = SOCK_STREAM;
+	char portstr[16];
+	snprintf(portstr, sizeof(portstr), "%d", portnr);
+	int rv = getaddrinfo(hostname, portstr, &hints, &res);
+	if (rv != 0) {
+		fprintf(stderr, "%s: %s\n", hostname, gai_strerror(rv));
 		return 2;
 	}
+	freeaddrinfo(res);
 
 	if (!quiet)
 		printf("tcping %s:%d\n", hostname, portnr);
@@ -116,7 +122,7 @@ int main(int argc, char *argv[])
 
 		for(;;)
 		{
-			fd = connect_to(hostdnsentries, portnr, timeout);
+			fd = connect_to(hostname, portnr, timeout);
 			if (fd == -1)
 			{
 				printf("error connecting to host: %s\n", strerror(errno));
@@ -141,7 +147,7 @@ int main(int argc, char *argv[])
 			min = min > ms ? ms : min;
 			max = max < ms ? ms : max;
 
-			printf("connected to %s:%d, seq=%d time=%.2f ms\n", hostname, portnr, curncount, (dend - dstart) * 1000.0);
+			printf("connected to %s:%d, seq=%d time=%.2f ms\n", hostname, portnr, curncount, ms);
 
 			break;
 		}
--- a/tcp.c
+++ b/tcp.c
@@ -1,6 +1,5 @@
 #include <sys/types.h>
 #include <sys/socket.h>
-#include <netinet/in.h>
 #include <netdb.h>
 #include <errno.h>
 #include <stdio.h>
@@ -10,50 +9,44 @@
 #include <sys/time.h>
 #include <fcntl.h>
 
-#include "tcp.h"
-
-#define incopy(a)       *((struct in_addr *)a)
-
-int connect_to(struct hostent *host, int portnr, int timeout)
+int connect_to(const char *hostname, int portnr, int timeout)
 {
-		int fd;
-		int loop;
-		struct sockaddr_in addr;
+		int fd = -1;
+		int rv;
+		char portstr[16];
+		struct addrinfo hints, *servinfo, *p;
 		struct timeval tv;
 
-		/* create socket */
-		fd = socket(AF_INET, SOCK_STREAM, 0);
-		if (fd == -1)
-		{
-				perror("problem creating socket ");
-				exit(2);
+		snprintf(portstr, sizeof(portstr), "%d", portnr);
+
+		memset(&hints, 0, sizeof hints);
+		hints.ai_family = AF_UNSPEC;		// Allow IPv4 or IPv6
+		hints.ai_socktype = SOCK_STREAM;	// TCP
+
+		rv = getaddrinfo(hostname, portstr, &hints, &servinfo);
+		if (rv != 0) {
+			fprintf(stderr, "%s: %s\n", hostname, gai_strerror(rv));
+			return -1;
 		}
 
-		/* Set Socket Read-Write Timeout */
-		tv.tv_sec = timeout;
-		tv.tv_usec = 0;
-		setsockopt(fd, SOL_SOCKET, SO_SNDTIMEO, &tv, sizeof(tv));
-
-		/* initialize address structure */
-		memset((void *)&addr, 0, sizeof(addr));
-		addr.sin_port   = htons(portnr);
-		addr.sin_family = host -> h_addrtype;
-
-		/* try to connect for each of the entries: */
-		for(loop=0; ; loop++)
-		{
-				if ((host -> h_addr_list[loop]) == NULL)
-						break;
-
-				addr.sin_addr = incopy(host -> h_addr_list[loop]);
-				/* connect to peer */
-				if (connect(fd, (struct sockaddr *)&addr, sizeof(addr)) == 0)
-				{
-						/* connection made, return */
-						return fd;
-				}
+		for (p = servinfo; p != NULL; p = p->ai_next) {
+			fd = socket(p->ai_family, p->ai_socktype, p->ai_protocol);
+			if (fd == -1)
+				continue;
+
+			tv.tv_sec = timeout;
+			tv.tv_usec = 0;
+			setsockopt(fd, SOL_SOCKET, SO_SNDTIMEO, &tv, sizeof(tv));
+			setsockopt(fd, SOL_SOCKET, SO_RCVTIMEO, &tv, sizeof(tv));
+
+			if (connect(fd, p->ai_addr, p->ai_addrlen) == 0)
+				break;
+
+			close(fd);
+			fd = -1;
 		}
-		close(fd);
-		if (errno = EALREADY) errno = ETIMEDOUT;
-		return -1;
+
+		freeaddrinfo(servinfo);
+
+		return fd;
 }
--- a/tcp.h
+++ b/tcp.h
@@ -1 +1 @@
-int connect_to(struct hostent *host, int portnr, int timeout);
+int connect_to(const char *hostname, int portnr, int timeout);