cli: proper ipv6 support for cli interface

We had several flaws on server side that was breaking ipv6 cli support.
accel-pppd/cli/cli_p.h — three shared helpers used by both listeners: cli_parse_hostport() (accepts host:port, [ipv6]:port, bare ::1:port via last-colon split, and :port for wildcard), cli_bind_addr()
(builds an IPv4 or IPv6 sockaddr, modeled on the existing SSTP pattern), and cli_addr_str() (formats peer addresses for logging, including v4-mapped).
accel-pppd/cli/tcp.c and telnet.c — listeners now create a socket of whichever family the configured address is; client address storage switched from sockaddr_in to sockaddr_storage so connection logging prints IPv6 peers correctly.
An invalid address now logs an error instead of silently binding garbage (previously inet_addr() failure went unchecked). Also fixed a pre-existing quirk where the fd itself was passed as the SO_REUSEADDR option value.
accel-pppd/accel-ppp.conf.5 — documented the new [::1]:2000 syntax and [::]:port for the IPv6 wildcard.

Might fix: https://github.com/accel-ppp/accel-ppp/issues/317

Signed-off-by: Denys Fedoryshchenko <denys.f@collabora.com>

1 files changed, 84 insertions, 0 deletions

diff --git a/accel-pppd/cli/cli_p.h b/accel-pppd/cli/cli_p.h
index 0fcba309..79208e13 100644
--- a/accel-pppd/cli/cli_p.h
+++ b/accel-pppd/cli/cli_p.h
@@ -2,6 +2,11 @@
 #define __CLI_P_H
 
 #include <stdarg.h>
+#include <stdlib.h>
+#include <string.h>
+#include <arpa/inet.h>
+#include <netinet/in.h>
+#include <sys/socket.h>
 
 #include "triton.h"
 
@@ -15,6 +20,85 @@ struct cli_client_t
 
 int cli_process_cmd(struct cli_client_t *cln);
 
+/* Format peer address (IPv4, IPv6 or IPv4-mapped IPv6) for logging.
+ * buf must be at least INET6_ADDRSTRLEN bytes long. */
+static inline const char *cli_addr_str(const struct sockaddr_storage *addr,
+				       char *buf, size_t size)
+{
+	const struct sockaddr_in6 *sin6 = (const struct sockaddr_in6 *)addr;
+	const struct sockaddr_in *sin = (const struct sockaddr_in *)addr;
+
+	buf[0] = '\0';
+	if (addr->ss_family == AF_INET6) {
+		if (IN6_IS_ADDR_V4MAPPED(&sin6->sin6_addr))
+			inet_ntop(AF_INET, &sin6->sin6_addr.s6_addr32[3], buf, size);
+		else
+			inet_ntop(AF_INET6, &sin6->sin6_addr, buf, size);
+	} else
+		inet_ntop(AF_INET, &sin->sin_addr, buf, size);
+
+	return buf;
+}
+
+/* Parse "host:port", "[host]:port" or ":port" listener specification.
+ * str is modified in place, *host points into str afterwards (NULL for
+ * empty host). For unbracketed hosts the last ':' separates the port,
+ * so bare IPv6 addresses like "::1:2001" are accepted too.
+ * Returns 0 on success, -1 on invalid format. */
+static inline int cli_parse_hostport(char *str, const char **host, int *port)
+{
+	char *d;
+
+	if (*str == '[') {
+		++str;
+		d = strchr(str, ']');
+		if (!d || d[1] != ':')
+			return -1;
+		*d++ = '\0';
+	} else {
+		d = strrchr(str, ':');
+		if (!d)
+			return -1;
+	}
+
+	*d = '\0';
+	*port = atoi(d + 1);
+	if (*port <= 0)
+		return -1;
+
+	*host = *str ? str : NULL;
+
+	return 0;
+}
+
+/* Fill sockaddr for binding a CLI listener. host may be an IPv4 or IPv6
+ * address; NULL host means any IPv4 address (use "::" for IPv6 wildcard).
+ * Returns 0 on success, -1 if host is not a valid address. */
+static inline int cli_bind_addr(const char *host, int port,
+				struct sockaddr_storage *addr, socklen_t *len)
+{
+	struct sockaddr_in6 *sin6 = (struct sockaddr_in6 *)addr;
+	struct sockaddr_in *sin = (struct sockaddr_in *)addr;
+
+	memset(addr, 0, sizeof(*addr));
+
+	if (host && inet_pton(AF_INET6, host, &sin6->sin6_addr) > 0) {
+		sin6->sin6_family = AF_INET6;
+		sin6->sin6_port = htons(port);
+		*len = sizeof(*sin6);
+	} else {
+		sin->sin_family = AF_INET;
+		sin->sin_port = htons(port);
+		if (!host)
+			sin->sin_addr.s_addr = htonl(INADDR_ANY);
+		else if (inet_pton(AF_INET, host, &sin->sin_addr) <= 0)
+			return -1;
+		*len = sizeof(*sin);
+	}
+
+	return 0;
+}
+
 extern char *conf_cli_passwd;
 extern char *conf_cli_prompt;