[Tarantool-patches] [PATCH 14/15] sio: introduce and use sio_snprintf()

[Vladislav Shpilevoy via Tarantool-patches <tarantool-patches@dev.tarantool.org>]

sio_strfaddr() can't be used in the places where static buffer
is not acceptable - in any code which wants to push the value to
Lua, or the address string must be long living.

The patch introduces sio_snprintf(), which does the same, but
saves the result into a provided buffer with a limited size.

In the Lua C code the patch saves the address string on the stack
which makes it safe against Lua GC interruptions.

Part of #5632

(cherry picked from commit fde44b569bf920a08469b9569eab1701d4e57299)
---
 src/box/lua/session.c |  7 +++++--
 src/sio.cc            | 38 +++++++++++++++++++++++++-------------
 src/sio.h             |  5 +++++
 3 files changed, 35 insertions(+), 15 deletions(-)

diff --git a/src/box/lua/session.c b/src/box/lua/session.c
index d1d0da2d2..26315bc4b 100644
--- a/src/box/lua/session.c
+++ b/src/box/lua/session.c
@@ -264,10 +264,13 @@ lbox_session_peer(struct lua_State *L)
 
 	struct sockaddr_storage addr;
 	socklen_t addrlen = sizeof(addr);
-	if (sio_getpeername(fd, (struct sockaddr *)&addr, &addrlen) < 0)
+	struct sockaddr *addr_base = (struct sockaddr *)&addr;
+	if (sio_getpeername(fd, addr_base, &addrlen) < 0)
 		luaL_error(L, "session.peer(): getpeername() failed");
 
-	lua_pushstring(L, sio_strfaddr((struct sockaddr *)&addr, addrlen));
+	char addrbuf[SERVICE_NAME_MAXLEN];
+	sio_addr_snprintf(addrbuf, sizeof(addrbuf), addr_base, addrlen);
+	lua_pushstring(L, addrbuf);
 	return 1;
 }
 
diff --git a/src/sio.cc b/src/sio.cc
index a425b8383..1f7800d6d 100644
--- a/src/sio.cc
+++ b/src/sio.cc
@@ -62,16 +62,17 @@ sio_socketname_to_buffer(int fd, char *buf, int size)
 		return 0;
 	struct sockaddr_storage addr;
 	socklen_t addrlen = sizeof(addr);
-	int rc = getsockname(fd, (struct sockaddr *) &addr, &addrlen);
+	struct sockaddr *base_addr = (struct sockaddr *)&addr;
+	int rc = getsockname(fd, base_addr, &addrlen);
 	if (rc == 0) {
-		SNPRINT(n, snprintf, buf, size, ", aka %s",
-			sio_strfaddr((struct sockaddr *)&addr, addrlen));
+		SNPRINT(n, snprintf, buf, size, ", aka ");
+		SNPRINT(n, sio_addr_snprintf, buf, size, base_addr, addrlen);
 	}
 	addrlen = sizeof(addr);
 	rc = getpeername(fd, (struct sockaddr *) &addr, &addrlen);
 	if (rc == 0) {
-		SNPRINT(n, snprintf, buf, size, ", peer of %s",
-			sio_strfaddr((struct sockaddr *)&addr, addrlen));
+		SNPRINT(n, snprintf, buf, size, ", peer of ");
+		SNPRINT(n, sio_addr_snprintf, buf, size, base_addr, addrlen);
 	}
 	return 0;
 }
@@ -510,26 +511,37 @@ sio_getpeername(int fd, struct sockaddr *addr, socklen_t *addrlen)
 }
 
 /** Pretty print a peer address. */
-const char *
-sio_strfaddr(struct sockaddr *addr, socklen_t addrlen)
+int
+sio_addr_snprintf(char *buf, size_t size, const struct sockaddr *addr,
+		  socklen_t addrlen)
 {
-	static __thread char name[NI_MAXHOST + _POSIX_PATH_MAX + 2];
+	int res;
 	if (addr->sa_family == AF_UNIX) {
 		struct sockaddr_un *u = (struct sockaddr_un *)addr;
 		if (addrlen >= sizeof(*u))
-			snprintf(name, sizeof(name), "unix/:%s", u->sun_path);
+			res = snprintf(buf, size, "unix/:%s", u->sun_path);
 		else
-			snprintf(name, sizeof(name), "unix/:(socket)");
+			res = snprintf(buf, size, "unix/:(socket)");
 	} else {
 		char host[NI_MAXHOST], serv[NI_MAXSERV];
 		int flags = NI_NUMERICHOST | NI_NUMERICSERV;
 		if (getnameinfo(addr, addrlen, host, sizeof(host),
 				serv, sizeof(serv), flags) != 0)
-			snprintf(name, sizeof(name), "(host):(port)");
+			res = snprintf(buf, size, "(host):(port)");
 		else if (addr->sa_family == AF_INET)
-			snprintf(name, sizeof(name), "%s:%s", host, serv);
+			res = snprintf(buf, size, "%s:%s", host, serv);
 		else
-			snprintf(name, sizeof(name), "[%s]:%s", host, serv);
+			res = snprintf(buf, size, "[%s]:%s", host, serv);
 	}
+	assert(res + 1 < SERVICE_NAME_MAXLEN);
+	assert(res >= 0);
+	return res;
+}
+
+const char *
+sio_strfaddr(struct sockaddr *addr, socklen_t addrlen)
+{
+	static __thread char name[SERVICE_NAME_MAXLEN];
+	sio_addr_snprintf(name, sizeof(name), addr, addrlen);
 	return name;
 }
diff --git a/src/sio.h b/src/sio.h
index 3b91f7eee..262bfcab8 100644
--- a/src/sio.h
+++ b/src/sio.h
@@ -57,6 +57,11 @@ enum {
 	SERVICE_NAME_MAXLEN = 200,
 };
 
+/** Format the address into the given buffer. Behaves like snprintf(). */
+int
+sio_addr_snprintf(char *buf, size_t size, const struct sockaddr *addr,
+		  socklen_t addrlen);
+
 const char *
 sio_strfaddr(struct sockaddr *addr, socklen_t addrlen);
 
-- 
2.24.3 (Apple Git-128)