add to osmo_sock_get_name*() API

Basically, I am applying code review that I would have given had I not been on
vacation when the last osmo_sock_get_name* stuff was merged.

osmo_sock_get_name2() is so far a static internal function. However, it is
nothing like osmo_sock_get_name(), so instead rename it to
osmo_sock_get_ip_and_port(). Also make it public API, no need to hide it.  I'm
adding an "and" in the name to hopefully clarify: "ip_port" vs. "ip_and_port"
-- there already are _get_X_ip_port() functions that only return the port
string, despite "ip" in the name.

Add new public osmo_sock_get_name2(), which is like osmo_sock_get_name(),
except it uses a static string instead of talloc, and omits the braces. This
is most convenient for log statement formats, avoiding dyn allocations.

Add new osmo_sock_get_name_buf(), which is like osmo_sock_get_name2() but
writes to a caller provided char buffer.

Use osmo_sock_get_name_buf() in the implementation of osmo_sock_get_name(),
but use another (non-static) local string buffer, because adding braces is too
complex without talloc_snprintf().

Rationale:

I want to improve the logging of socket errors, e.g. change

  DLMGCP ERROR Failed to read: 111/Connection refused (mgcp_client.c:720)

to

  DLMGCP ERROR Failed to read: r=10.0.99.2:2427<->l=10.0.99.2:2728: 111='Connection refused' (mgcp_client.c:721)

but it is just not handy to compose logging with the current API:

- osmo_sock_get_name() requires a talloc_free().
- all the others require output buffers.
- the only way to conveniently compose a logging string and,
- notably, the only trivial way to skip the string composition if the logging
  level is currently muted, is to have a function that returns a static string:
  the new osmo_sock_get_name2().
- (I think the osmo_sock_get_{local,remote}_* convenience wrappers should never
  have been added, because they encourage the caller to invoke the same code
  twice, for IP addr and port, and throw away one half each time.)

Related: Iae728192f499330d16836d9435648f6b8ed213b6 (osmo-mgw)
Change-Id: I8ad89ac447c9c582742e70d082072bdd40a5a398

2 files changed, 50 insertions, 17 deletions

diff --git a/include/osmocom/core/socket.h b/include/osmocom/core/socket.h
index 79a61bb0..43604ec0 100644
--- a/include/osmocom/core/socket.h
+++ b/include/osmocom/core/socket.h
@@ -60,6 +60,9 @@ int osmo_sock_unix_init_ofd(struct osmo_fd *ofd, uint16_t type, uint8_t proto,
 			    const char *socket_path, unsigned int flags);
 
 char *osmo_sock_get_name(void *ctx, int fd);
+const char *osmo_sock_get_name2(int fd);
+int osmo_sock_get_name_buf(char *str, size_t str_len, int fd);
+int osmo_sock_get_ip_and_port(int fd, char *ip, size_t ip_len, char *port, size_t port_len, bool local);
 int osmo_sock_get_local_ip(int fd, char *host, size_t len);
 int osmo_sock_get_local_ip_port(int fd, char *port, size_t len);
 int osmo_sock_get_remote_ip(int fd, char *host, size_t len);
diff --git a/src/socket.c b/src/socket.c
index e804ab53..4f3b1cab 100644
--- a/src/socket.c
+++ b/src/socket.c
@@ -697,10 +697,7 @@ int osmo_sock_unix_init_ofd(struct osmo_fd *ofd, uint16_t type, uint8_t proto,
 	return osmo_fd_init_ofd(ofd, osmo_sock_unix_init(type, proto, socket_path, flags));
 }
 
-/*! Get the IP and/or port number on socket. This is for internal usage.
- *  Convenience wrappers: osmo_sock_get_local_ip(),
- *  osmo_sock_get_local_ip_port(), osmo_sock_get_remote_ip(),
- *  osmo_sock_get_remote_ip_port() and osmo_sock_get_name()
+/*! Get the IP and/or port number on socket in separate string buffers.
  *  \param[in] fd file descriptor of socket
  *  \param[out] ip IP address (will be filled in when not NULL)
  *  \param[in] ip_len length of the ip buffer
@@ -709,7 +706,7 @@ int osmo_sock_unix_init_ofd(struct osmo_fd *ofd, uint16_t type, uint8_t proto,
  *  \param[in] local (true) or remote (false) name will get looked at
  *  \returns 0 on success; negative otherwise
  */
-static int osmo_sock_get_name2(int fd, char *ip, size_t ip_len, char *port, size_t port_len, bool local)
+int osmo_sock_get_ip_and_port(int fd, char *ip, size_t ip_len, char *port, size_t port_len, bool local)
 {
 	struct sockaddr sa;
 	socklen_t len = sizeof(sa);
@@ -741,7 +738,7 @@ static int osmo_sock_get_name2(int fd, char *ip, size_t ip_len, char *port, size
  */
 int osmo_sock_get_local_ip(int fd, char *ip, size_t len)
 {
-	return osmo_sock_get_name2(fd, ip, len, NULL, 0, true);
+	return osmo_sock_get_ip_and_port(fd, ip, len, NULL, 0, true);
 }
 
 /*! Get local port on socket
@@ -752,7 +749,7 @@ int osmo_sock_get_local_ip(int fd, char *ip, size_t len)
  */
 int osmo_sock_get_local_ip_port(int fd, char *port, size_t len)
 {
-	return osmo_sock_get_name2(fd, NULL, 0, port, len, true);
+	return osmo_sock_get_ip_and_port(fd, NULL, 0, port, len, true);
 }
 
 /*! Get remote IP address on socket
@@ -763,7 +760,7 @@ int osmo_sock_get_local_ip_port(int fd, char *port, size_t len)
  */
 int osmo_sock_get_remote_ip(int fd, char *ip, size_t len)
 {
-	return osmo_sock_get_name2(fd, ip, len, NULL, 0, false);
+	return osmo_sock_get_ip_and_port(fd, ip, len, NULL, 0, false);
 }
 
 /*! Get remote port on socket
@@ -774,29 +771,62 @@ int osmo_sock_get_remote_ip(int fd, char *ip, size_t len)
  */
 int osmo_sock_get_remote_ip_port(int fd, char *port, size_t len)
 {
-	return osmo_sock_get_name2(fd, NULL, 0, port, len, false);
+	return osmo_sock_get_ip_and_port(fd, NULL, 0, port, len, false);
 }
 
-/*! Get address/port information on socket in dyn-alloc string
+/*! Get address/port information on socket in dyn-alloc string like "(r=1.2.3.4:5<->l=6.7.8.9:10)".
+ * Usually, it is better to use osmo_sock_get_name2() for a static string buffer or osmo_sock_get_name_buf() for a
+ * caller provided string buffer, to avoid the dynamic talloc allocation.
  *  \param[in] ctx talloc context from which to allocate string buffer
  *  \param[in] fd file descriptor of socket
- *  \returns string identifying the connection of this socket
+ *  \returns string identifying the connection of this socket, talloc'd from ctx.
  */
 char *osmo_sock_get_name(void *ctx, int fd)
 {
+	/* "r=1.2.3.4:123<->l=5.6.7.8:987" */
+	char str[2 + INET6_ADDRSTRLEN + 1 + 5 + 3 + 2 + INET6_ADDRSTRLEN + 1 + 5 + 1];
+	int rc;
+	rc = osmo_sock_get_name_buf(str, sizeof(str), fd);
+	if (rc <= 0)
+		return NULL;
+	return talloc_asprintf(ctx, "(%s)", str);
+}
+
+/*! Get address/port information on socket in provided string buffer, like "r=1.2.3.4:5<->l=6.7.8.9:10".
+ * This does not include braces like osmo_sock_get_name().
+ *  \param[out] str  Destination string buffer.
+ *  \param[in] str_len  sizeof(str).
+ *  \param[in] fd  File descriptor of socket.
+ *  \return String length as returned by snprintf(), or negative on error.
+ */
+int osmo_sock_get_name_buf(char *str, size_t str_len, int fd)
+{
 	char hostbuf_l[INET6_ADDRSTRLEN], hostbuf_r[INET6_ADDRSTRLEN];
 	char portbuf_l[6], portbuf_r[6];
+	int rc;
 
 	/* get local */
-	if (osmo_sock_get_name2(fd, hostbuf_l, sizeof(hostbuf_l), portbuf_l, sizeof(portbuf_l), true))
-		return NULL;
+	if ((rc = osmo_sock_get_ip_and_port(fd, hostbuf_l, sizeof(hostbuf_l), portbuf_l, sizeof(portbuf_l), true)))
+		return rc;
 
 	/* get remote */
-	if (!osmo_sock_get_name2(fd, hostbuf_r, sizeof(hostbuf_r), portbuf_r, sizeof(portbuf_r), false))
-		return talloc_asprintf(ctx, "(r=%s:%s<->l=%s:%s)", hostbuf_r, portbuf_r, hostbuf_l, portbuf_l);
+	if (osmo_sock_get_ip_and_port(fd, hostbuf_r, sizeof(hostbuf_r), portbuf_r, sizeof(portbuf_r), false) != 0)
+		return snprintf(str, str_len, "r=NULL<->l=%s:%s", hostbuf_l, portbuf_l);
+
+	return snprintf(str, str_len, "r=%s:%s<->l=%s:%s", hostbuf_r, portbuf_r, hostbuf_l, portbuf_l);
+}
 
-	/* local only: different format */
-	return talloc_asprintf(ctx, "(r=NULL<->l=%s:%s)", hostbuf_l, portbuf_l);
+/*! Get address/port information on socket in static string, like "r=1.2.3.4:5<->l=6.7.8.9:10".
+ * This does not include braces like osmo_sock_get_name().
+ *  \param[in] fd  File descriptor of socket.
+ *  \return Static string buffer containing the result.
+ */
+const char *osmo_sock_get_name2(int fd)
+{
+	/* "r=1.2.3.4:123<->l=5.6.7.8:987" */
+	static char str[2 + INET6_ADDRSTRLEN + 1 + 5 + 3 + 2 + INET6_ADDRSTRLEN + 1 + 5 + 1];
+	osmo_sock_get_name_buf(str, sizeof(str), fd);
+	return str;
 }
 
 static int sock_get_domain(int fd)