1 files changed, 107 insertions, 0 deletions
diff --git a/noport.c b/noport.c
new file mode 100644
index 0000000..c7a0c01
--- /dev/null
+++ b/noport.c
@@ -0,0 +1,107 @@
+#define _GNU_SOURCE
+#include <sys/socket.h>
+#include <dlfcn.h>
+#include <errno.h>
+#include <stdlib.h>
+#include <string.h>
+#include <netinet/in.h>
+
+static int
+port_is_okay(unsigned short port)
+{
+	char *p, *q;
+	long l;
+
+	p = getenv("NOPORT");
+	while ((p != NULL) && (*p != '\0')) {
+		l = strtol(p, &q, 10);
+		if ((q == NULL) || (q == p)) {
+			break;
+		}
+		if ((*q == '\0') || (*q == ',')) {
+			if (port == l) {
+				errno = ECONNREFUSED;
+				return -1;
+			}
+		}
+		p = q;
+		p += strspn(p, ",");
+	}
+	return 0;
+}
+
+int
+connect(int sockfd, const struct sockaddr *addr, socklen_t addrlen)
+{
+	unsigned short port;
+	static int (*next_connect)(int, const struct sockaddr *, socklen_t);
+
+	if (next_connect == NULL) {
+		next_connect = dlsym(RTLD_NEXT, "connect");
+		if (next_connect == NULL) {
+			errno = ENOSYS;
+			return -1;
+		}
+	}
+
+	if (getenv("NOPORT") == NULL) {
+		return next_connect(sockfd, addr, addrlen);
+	}
+
+	switch (addr->sa_family) {
+	case AF_INET:
+		port = ntohs(((struct sockaddr_in *)addr)->sin_port);
+		if (port_is_okay(port) != 0) {
+			return -1;
+		}
+		break;
+	case AF_INET6:
+		port = ntohs(((struct sockaddr_in6 *)addr)->sin6_port);
+		if (port_is_okay(port) != 0) {
+			return -1;
+		}
+		break;
+	default:
+		break;
+	}
+	return next_connect(sockfd, addr, addrlen);
+}
+
+ssize_t
+sendto(int sockfd, const void *buf, size_t len, int flags,
+       const struct sockaddr *dest_addr, socklen_t addrlen)
+{
+	unsigned short port;
+	static int (*next_sendto)(int, const void *, size_t, int,
+				  const struct sockaddr *, socklen_t);
+
+	if (next_sendto == NULL) {
+		next_sendto = dlsym(RTLD_NEXT, "sendto");
+		if (next_sendto == NULL) {
+			errno = ENOSYS;
+			return -1;
+		}
+	}
+
+	if (getenv("NOPORT") == NULL) {
+		return next_sendto(sockfd, buf, len, flags, dest_addr, addrlen);
+	}
+
+	switch (dest_addr->sa_family) {
+	case AF_INET:
+		port = ntohs(((struct sockaddr_in *)dest_addr)->sin_port);
+		if (port_is_okay(port) != 0) {
+			return -1;
+		}
+		break;
+	case AF_INET6:
+		port = ntohs(((struct sockaddr_in6 *)dest_addr)->sin6_port);
+		if (port_is_okay(port) != 0) {
+			return -1;
+		}
+		break;
+	default:
+		break;
+	}
+	return next_sendto(sockfd, buf, len, flags, dest_addr, addrlen);
+}