flexnbd read/write: Switch to a non-blocking connect() to allow us to time these out

src/sockutil.c

@@ -1,7 +1,14 @@
+#include <unistd.h>
+#include <fcntl.h>
+
+#include <sys/types.h>
+#include <arpa/inet.h>
+#include <netinet/tcp.h>
+
 #include "sockutil.h"
 #include "util.h"
 
-size_t sockaddr_size(const struct sockaddr* sa)
+size_t sockaddr_size( const struct sockaddr* sa )
 {
 	size_t ret = 0;
 
@@ -17,7 +24,7 @@ size_t sockaddr_size(const struct sockaddr* sa)
 	return ret;
 }
 
-const char* sockaddr_address_string(const struct sockaddr* sa, char* dest, size_t len)
+const char* sockaddr_address_string( const struct sockaddr* sa, char* dest, size_t len )
 {
 	NULLCHECK( sa );
 	NULLCHECK( dest );
@@ -47,18 +54,35 @@ const char* sockaddr_address_string(const struct sockaddr* sa, char* dest, size_
 	return ret;
 }
 
-int sock_set_reuseaddr(int fd, int optval)
+int sock_set_reuseaddr( int fd, int optval )
 {
 	return setsockopt( fd, SOL_SOCKET, SO_REUSEADDR, &optval, sizeof(optval) );
 }
 
 /* Set the tcp_nodelay option */
-int sock_set_tcp_nodelay(int fd, int optval)
+int sock_set_tcp_nodelay( int fd, int optval )
 {
 	return setsockopt( fd, IPPROTO_TCP, TCP_NODELAY, &optval, sizeof(optval) );
 }
 
-int sock_try_bind(int fd, const struct sockaddr* sa)
+int sock_set_nonblock( int fd, int optval )
+{
+	int flags = fcntl( fd, F_GETFL );
+
+	if ( flags == -1 ) {
+		return -1;
+	}
+
+	if ( optval ) {
+		flags = flags | O_NONBLOCK;
+	} else {
+		flags = flags & (~O_NONBLOCK);
+	}
+
+	return fcntl( fd, F_SETFL, flags );
+}
+
+int sock_try_bind( int fd, const struct sockaddr* sa )
 {
 	int bind_result;
 	char s_address[256];
@@ -102,3 +126,87 @@ int sock_try_bind(int fd, const struct sockaddr* sa)
 	return bind_result;
 }
 
+int sock_try_select(int nfds, fd_set *readfds, fd_set *writefds, fd_set *exceptfds, struct timeval *timeout)
+{
+	int result;
+
+	do {
+		result = select(nfds, readfds, writefds, exceptfds, timeout);
+		if ( errno != EINTR ) {
+			break;
+		}
+
+	} while ( result == -1 );
+
+	return result;
+}
+
+int sock_try_connect( int fd, struct sockaddr* to, socklen_t addrlen, int wait )
+{
+	fd_set fds;
+	struct timeval tv = { wait, 0 };
+	int result = 0;
+
+	if ( sock_set_nonblock( fd, 1 ) == -1 ) {
+		warn( SHOW_ERRNO( "Failed to set socket non-blocking for connect()" ) );
+		return connect( fd, to, addrlen );
+	}
+
+	FD_ZERO( &fds );
+	FD_SET( fd, &fds );
+
+	do {
+		result = connect( fd, to, addrlen );
+
+		if ( result == -1 ) {
+			switch( errno ) {
+				case EINPROGRESS:
+					result = 0;
+					break; /* success */
+				case EAGAIN:
+				case EINTR:
+					break; /* Try again */
+				default:
+					warn( SHOW_ERRNO( "Failed to connect()") );
+					goto out;
+			}
+		}
+	} while ( result == -1 );
+
+	if ( -1 == sock_try_select( FD_SETSIZE, NULL, &fds, NULL, &tv) ) {
+		warn( SHOW_ERRNO( "failed to select() on non-blocking connect" ) );
+		result = -1;
+		goto out;
+	}
+
+	if ( !FD_ISSET( fd, &fds ) ) {
+		result = -1;
+		errno = ETIMEDOUT;
+		goto out;
+	}
+
+	int scratch;
+	socklen_t s_size = sizeof( scratch );
+	if ( getsockopt( fd, SOL_SOCKET, SO_ERROR, &scratch, &s_size ) == -1 ) {
+		result = -1;
+		warn( SHOW_ERRNO( "getsockopt() failed" ) );
+		goto out;
+	}
+
+	if ( scratch == EINPROGRESS ) {
+		scratch = ETIMEDOUT;
+	}
+
+	result = scratch ? -1 : 0;
+	errno = scratch;
+
+out:
+	if ( sock_set_nonblock( fd, 0 ) == -1 ) {
+		warn( SHOW_ERRNO( "Failed to make socket blocking after connect()" ) );
+		return -1;
+	}
+
+	debug( "sock_try_connect: %i", result );
+	return result;
+}
+