Make I/O non-blocking, add --timeout parameter.

Thank you to DL9SEC for reporting a strange case.  The IGate server
cwop.aprs2.net has multiple IP addresses defined in DNS, and not all
of them work.  This causes aprs-weather-submit to hang.  This commit
converts all socket operations to non-blocking.

I've also added a new --timeout parameter that can specify how many
seconds the app will wait before trying the next IPv4/IPv6 address,
or failing.  The default is 15 seconds, because that sounded nice.

This does add a few kilobytes to the compiled app, so I may wrap this
in a `#ifdef ONLY_BLOCKING_IO` or something.

I'm still wondering if this is major-enough change to warrant a bump
of the version number to 2.0.0.

Fixes: #12

CHANGELOG.md

@@ -1,6 +1,8 @@
 # Change Log for `aprs-weather-submit`
 
 ## Latest changes
+*   Converted the APRS-IS socket from blocking to non-blocking, with a default timeout of 15 seconds before the connection is aborted.
+*   Added a new parameter, `--timeout`, to set how long the app will wait for the remote server before giving up.
 *   Added support for ISO-compliant compilers (e.g., `gcc -pedantic`).
 *   Fixed a bug where `./configure --disable-aprs-is` was not honored.
 

NEWS.md

@@ -2,20 +2,16 @@
 
 This file details all of the user-facing changes that are in versions 1.7 of aprs-weather-submit. For more details, please consult the CHANGELOG file or this project's GitHub page.
 
-## Custom Icons
+## Graceful failure
 
-The new `--icon` parameter lets you specify a character from the two symbol tables.  If not specified, you will get the classic weather icon.
+In version 1.7.2 and older, the app would hang almost indefinitely if the remote APRS-IS server did not respond.  This version fixes that by converting to non-blocking sockets, so that if your APRS-IS server does not respond in a timely manner (for whatever reason), the connection will fail gracefully.
 
-Note that APRS.fi does not support parsing weather data from packets that have custom icons.  If this is important to you, do not use this new feature.
+Likewise, there is a new parameter, `--timeout`, that will let you specify a timeout value, if you don't like my default of fifteen seconds.
 
-## `armhf` Fixes
+If you want the old behavior, specify `--timeout 0`.
 
-Version 1.7 did not compile on the armhf platforms.  Version 1.7.1 is fixed.
 
-## It's not the heat, it's the humidity!
+## Building without APRS-IS support
 
-Before version 1.7.2, one could not create an APRS packet with 100% relative humidity due to a bug in the code that only allowed values from 1% to 99%.  This was corrected in version 1.7.2 thanks to a report from Jeff, N9CQS.
+I'd always given users the option to build a custom version without APRS-IS support by specifying `./configure --disable-aprs-is`.  However, that broke at some point.  This option now works as intended.
 
-## Can this app be in Debian, please?
-
-I've also been making behind-the-scenes improvements to how this app is packaged and installed.  Users of Debian-based Linux distributions can enjoy nearly-effortless installation, upgrades, and removals.

configure.ac

@@ -132,6 +132,11 @@ dnl need: [gai_strerror getaddrinfo inet_ntop ntohs perror recv send shutdown so
         [],
         AC_MSG_ERROR([Cannot compile with APRS-IS support because <unistd.h> is missing.])
     )
+    AC_CHECK_FUNC(
+        [atol],
+        [],
+        AC_MSG_ERROR([atol() is required to build this package but was not found in stdlib.h.])
+    )
     AS_IF([test "x$enable_windows" != "xyes"], [
         AC_CHECK_HEADERS(
             [arpa/inet.h],

man/aprs-weather-submit.man

@@ -18,7 +18,7 @@
 .\"
 .\" (This page is best viewed with the command: groff -man)
 .\"
-.TH aprs\-weather\-submit 1 "2023-11-30" "Version 1.7.1" "aprs-weather-submit General Help"
+.TH aprs\-weather\-submit 1 "2024-10-29" "Version 1.7.2-git" "aprs-weather-submit General Help"
 .SH NAME
 aprs\-weather\-submit \- manually submit weather station data to the APRS-IS network
 .SH DESCRIPTION
@@ -34,6 +34,8 @@ This command-line app will manually submit APRS 1.2.1-compliant weather informat
 [
 .BI "\-I " SERVER_NAME " \-o " PORT_NUMBER " \-u " USERNAME " \-d " PASSWORD
 ]
+.RB [ " \-m "
+.IR SECONDS " ]\:"
 .RB [ " \-A "
 .IR FEET " ]\:"
 .RB [ " \-b "
@@ -145,6 +147,16 @@ Authenticate to the server with this password.
 Note that this will be sent in cleartext!
 (See the BUGS AND ERRATA section.)
 
+.SS OPTIONAL APRS-IS OPTIONS
+By default, the app will wait 15 seconds for the IGate server to respond before giving up.
+.TP
+.BR \-m ", " \-\-timeout =\fISECONDS\fP
+Wait this many seconds before aborting the connection.
+The default is 15 seconds, but you may want to use a longer value over a slow Internet connection.
+.TP
+To wait forever and block until the server responds (or your operating system terminates the connection), specify a value of 0 seconds.
+This was the behavior in previous versions of the app.
+
 .SS WEATHER OPTIONS
 You may add zero or more weather measurements to your report.
 All minimum and maximum measurements listed below are inclusive unless otherwise specified.
@@ -298,7 +310,7 @@ APRS Version 1.2.1, "Weather Updates to the Spec" (24 Mar 2011)
 .UE
 
 .SH AUTHOR AND COPYRIGHT
-.BR aprs\-weather\-submit ", version 1.6"
+.BR aprs\-weather\-submit ", version 1.7.2-git"
 .br
 Copyright (c) 2019-2024 Colin Cogle.
 .br

src/aprs-is.c

@@ -26,11 +26,13 @@ with this program.  If not, see <https://www.gnu.org/licenses/agpl-3.0.html>.
 #include <string.h>     /* strcat() */
 #include "main.h"       /* PACKAGE, VERSION */
 #include "aprs-is.h"
+#include <errno.h>	/* errno */
 
 #ifndef _WIN32
 #include <sys/types.h>  /* size_t */
 #include <sys/socket.h> /* socket(), connect(), shutdown(), recv(), send() */
 #include <netinet/in.h> /* sockaddr, sockaddr_in, sockaddr_in6 */
+#include <netinet/tcp.h>/* TCP_USER_TIMEOUT */
 #include <arpa/inet.h>  /* inet_pton() */
 #include <netdb.h>      /* getaddrinfo(), gai_strerror() */
 #include <unistd.h>     /* EAI_SYSTEM */
@@ -45,6 +47,7 @@ with this program.  If not, see <https://www.gnu.org/licenses/agpl-3.0.html>.
  * @author         Colin Cogle
  * @param server   The DNS hostname of the server.
  * @param port     The listening port on the server.
+ * @param timeout  How long to wait before ending the connection.
  * @param username The username with which to authenticate to the server.
  * @param password The password with which to authenticate to the server.
  * @param toSend   The APRS-IS packet, as a string.
@@ -53,6 +56,7 @@ with this program.  If not, see <https://www.gnu.org/licenses/agpl-3.0.html>.
 void
 sendPacket (const char* const restrict server,
             const unsigned short port,
+            const time_t timeout,
             const char* const restrict username,
             const char* const restrict password,
             const char* const restrict toSend)
@@ -124,6 +128,14 @@ sendPacket (const char* const restrict server,
 		}
 
 		/* Connect */
+		char* timeoutText = malloc(BUFSIZE);
+		sprintf(timeoutText, " (timeout %ld seconds)", timeout);
+
+		if (timeout <= 0)
+		{
+			strncpy(timeoutText, " (no timeout)", BUFSIZE);
+		}
+
 		switch (addressinfo->sa_family)
 		{
 			case AF_INET:
@@ -133,22 +145,41 @@ sendPacket (const char* const restrict server,
 					buffer,
 					INET_ADDRSTRLEN);
 #ifdef DEBUG
-				printf("Connecting to %s:%d...\n", buffer,
-				       ntohs(((struct sockaddr_in*)addressinfo)->sin_port));
+				printf("Connecting to %s:%d%s...\n",
+				       buffer,
+				       ntohs(((struct sockaddr_in*)addressinfo)->sin_port),
+				       timeoutText
+				);
 #endif
 				break;
+
 			case AF_INET6:
 				inet_ntop(
 					AF_INET6,
 					&((struct sockaddr_in6*)addressinfo)->sin6_addr,
 					buffer,
 					INET6_ADDRSTRLEN);
 #ifdef DEBUG
-				printf("Connecting to [%s]:%d...\n", buffer,
-				       ntohs(((struct sockaddr_in6*)addressinfo)->sin6_port));
+				printf("Connecting to [%s]:%d%s...\n",
+				       buffer,
+				       ntohs(((struct sockaddr_in6*)addressinfo)->sin6_port),
+				       timeoutText
+				);
 #endif
 				break;
 		}
+		free(timeoutText);
+
+		/* Code to handle timeouts, as long as the user doesn't
+		   want to wait forever (like v1.7.2 and older). */
+		if (timeout > 0)
+		{
+			struct timeval socket_timeout;
+			socket_timeout.tv_sec  = timeout;
+			socket_timeout.tv_usec = 0;
+			setsockopt(socket_desc, SOL_SOCKET, SO_SNDTIMEO, &socket_timeout, sizeof(socket_timeout));
+			setsockopt(socket_desc, SOL_SOCKET, SO_RCVTIMEO, &socket_timeout, sizeof(socket_timeout));
+		}
 
 		if (connect(socket_desc, addressinfo, (size_t)(result->ai_addrlen)) >= 0)
 		{
@@ -157,6 +188,14 @@ sendPacket (const char* const restrict server,
 		}
 		else
 		{
+			/* The error message for a timeout is misleading.
+			   It says the connection is in progress, but we
+			   are going to kill it, so this next statement
+			   replaces that error with something clearer. */
+			if (errno == EINPROGRESS)
+			{
+				errno = ETIMEDOUT;
+			}
 			perror("error in connect()");
 			shutdown(socket_desc, 2);
 		}
@@ -207,7 +246,7 @@ sendPacket (const char* const restrict server,
 	printf("> %s", toSend);
 #endif
 	send(socket_desc, toSend, (size_t)strlen(toSend), 0);
-	
+
 	/* Done! */
 	shutdown(socket_desc, 2);
 	return;

src/aprs-is.h

@@ -30,17 +30,26 @@ with this program.  If not, see <https://www.gnu.org/licenses/agpl-3.0.html>.
  * @author         Colin Cogle
  * @param server   The DNS hostname of the server.
  * @param port     The listening port on the server.
+ * @param timeout  How long to wait before timing out.
  * @param username The username with which to authenticate to the server.
  * @param password The password with which to authenticate to the server.
  * @param toSend   The APRS-IS packet, as a string.
  * @since 0.3
  */
 void
-sendPacket (const char* const restrict server, const unsigned short port,
+sendPacket (const char* const restrict server,
+            const unsigned short port,
+            const time_t timeout,
             const char* const restrict username,
             const char* const restrict password,
             const char* const restrict toSend);
 
+/* How long to wait before timing out when the user doesn't specify.
+   Fifteen seconds seems reasonable. */
+#ifndef DEFAULT_TIMEOUT
+#define DEFAULT_TIMEOUT 15
+#endif
+
 /* This should be defined by the operating system, but just in case... */
 #ifndef NI_MAXHOST
 #define NI_MAXHOST 1025

src/help.c

@@ -98,6 +98,7 @@ Required parameters:\n\
 	puts("APRS-IS IGate parameters:\n\
 	-I, --server        Name of the APRS-IS IGate server to submit the packet to.\n\
 	-o, --port          Port that the APRS-IS IGate service is listening on.\n\
+	-m, --timeout       How many seconds to wait for a connection.\n\
 	-u, --username      Authenticate to the server with this username.\n\
 	-d, --password      Authenticate to the server with this password.\n");
 #endif /* HAVE_APRSIS_SUPPORT */

src/main.c

@@ -61,6 +61,7 @@ main (const int argc, const char** argv)
 	char         username[BUFSIZE] = "";
 	char         password[BUFSIZE] = "";
 	char         server[NI_MAXHOST] = "";
+	time_t       timeout = DEFAULT_TIMEOUT;
 	uint16_t     port = 0;
 #endif
 
@@ -75,6 +76,7 @@ main (const int argc, const char** argv)
 #ifdef HAVE_APRSIS_SUPPORT
 		{"server",                  required_argument, 0, 'I'},
 		{"port",                    required_argument, 0, 'o'},
+		{"timeout",                 required_argument, 0, 'm'},
 		{"username",                required_argument, 0, 'u'},
 		{"password",                required_argument, 0, 'd'},
 #endif
@@ -131,8 +133,10 @@ main (const int argc, const char** argv)
 
 #ifdef _DOS
 	while ((c = (char) getopt(argc, (char**)argv, "CH?vI:o:u:d:k:n:e:A:c:S:g:t:T:r:P:p:s:h:b:L:X:F:V:QM:i:")) != -1)
+#elif HAVE_APRSIS_SUPPORT
+	while ((c = (char) getopt_long(argc, (char* const*)argv, "CHvI:o:m:u:d:k:n:e:A:c:S:g:t:T:r:P:p:s:h:b:L:X:F:V:QM:i:", long_options, &option_index)) != -1)
 #else
-	while ((c = (char) getopt_long(argc, (char* const*)argv, "CHvI:o:u:d:k:n:e:A:c:S:g:t:T:r:P:p:s:h:b:L:X:F:V:QM:i:", long_options, &option_index)) != -1)
+	while ((c = (char) getopt_long(argc, (char* const*)argv, "CHvk:n:e:A:c:S:g:t:T:r:P:p:s:h:b:L:X:F:V:QM:i:", long_options, &option_index)) != -1)
 #endif
 	{
 		double x = 0.0;	 /* scratch space */
@@ -182,6 +186,11 @@ main (const int argc, const char** argv)
 				port = (unsigned short)x;
 				break;
 
+			/* IGate server timeout (-m | --timeout) */
+			case 'm':
+				timeout = (time_t)atol(optarg);
+				break;
+
 			/* IGate server username (-u | --username) */
 			case 'u':
 				snprintf_verify(
@@ -646,7 +655,7 @@ main (const int argc, const char** argv)
 	 */
 	if (strlen(server) && strlen(username) && strlen(password) && port != 0)
 	{
-		sendPacket(server, port, username, password, packetToSend);
+		sendPacket(server, port, timeout, username, password, packetToSend);
 	}
 	else
 	{