librdmacm: Add support for dup

Add preload interception for dup so that duplicating an rsocket file
descriptor produces another rsocket fd that refers to the same connection.

Signed-off-by: Batsheva Black <bblack@nvidia.com>

Author: BatshevaBlack

librdmacm/librspreload.map

@@ -8,6 +8,7 @@
 		bind;
 		close;
 		connect;
+		dup;
 		dup2;
 		fcntl;
 		fcntl64;

librdmacm/preload.c

@@ -103,6 +103,7 @@ struct socket_calls {
 	(!defined(RDMA_PRELOAD_HAVE_64) || RDMA_PRELOAD_HAVE_64)
 	int (*fcntl64)(int socket, int cmd, ... /* arg */);
 #endif
+	int (*dup)(int oldfd);
 	int (*dup2)(int oldfd, int newfd);
 	ssize_t (*sendfile)(int out_fd, int in_fd, off_t *offset, size_t count);
 #if (!defined(_FILE_OFFSET_BITS) || _FILE_OFFSET_BITS != 64) && \
@@ -441,6 +442,7 @@ static void init_preload(void)
 (!defined(RDMA_PRELOAD_HAVE_64) || RDMA_PRELOAD_HAVE_64)
 	real.fcntl64 = dlsym(RTLD_NEXT, "fcntl64");
 #endif
+	real.dup = dlsym(RTLD_NEXT, "dup");
 	real.dup2 = dlsym(RTLD_NEXT, "dup2");
 	real.sendfile = dlsym(RTLD_NEXT, "sendfile");
 #if (!defined(_FILE_OFFSET_BITS) || _FILE_OFFSET_BITS != 64) && \
@@ -1243,6 +1245,13 @@ int fcntl64(int socket, int cmd, ... /* arg */)
 }
 #endif
 
+int dup(int oldfd)
+{
+	int new_fd = fcntl(oldfd, F_DUPFD, 0);
+
+	return dup2(oldfd, new_fd);
+}
+
 /*
  * dup2 is not thread safe
  */