X-Git-Url: http://git.tuebingen.mpg.de/?p=paraslash.git;a=blobdiff_plain;f=net.c;h=fa9575a6e5a6aa7d857777e1ea85d5f52ec05c01;hp=64693bef51e1b339f398cada9cb07ef3b0c8f05f;hb=72d73eb53316768a5a3527cf56afad7158d9ef4d;hpb=8a63543fdfbd3b5d00e4afecfbc397795a49ed04

diff --git a/net.c b/net.c
index 64693bef..fa9575a6 100644
--- a/net.c
+++ b/net.c
@@ -521,6 +521,14 @@ static socklen_t salen(const struct sockaddr *sa)
 		: sizeof(struct sockaddr_in);
 }
 
+/** True if @ss holds a v6-mapped-v4 address (RFC 4291, 2.5.5.2) */
+static bool SS_IS_ADDR_V4MAPPED(const struct sockaddr_storage *ss)
+{
+	const struct sockaddr_in6 *ia6 = (const struct sockaddr_in6 *)ss;
+
+	return ss->ss_family == AF_INET6 && IN6_IS_ADDR_V4MAPPED(&ia6->sin6_addr);
+}
+
 /**
  * Process IPv4/v6 address, turn v6-mapped-v4 address into normal IPv4 address.
  * \param ss Container of IPv4/6 address.
@@ -531,11 +539,10 @@ static socklen_t salen(const struct sockaddr *sa)
 static const struct sockaddr *
 normalize_ip_address(const struct sockaddr_storage *ss)
 {
-	const struct sockaddr_in6 *ia6 = (const struct sockaddr_in6 *)ss;
-
 	assert(ss->ss_family == AF_INET || ss->ss_family == AF_INET6);
 
-	if (ss->ss_family == AF_INET6 && IN6_IS_ADDR_V4MAPPED(&ia6->sin6_addr)) {
+	if (SS_IS_ADDR_V4MAPPED(ss)) {
+		const struct sockaddr_in6 *ia6 = (const struct sockaddr_in6 *)ss;
 		static struct sockaddr_in ia;
 
 		ia.sin_family = AF_INET;
@@ -546,6 +553,46 @@ normalize_ip_address(const struct sockaddr_storage *ss)
 	return (const struct sockaddr *)ss;
 }
 
+/**
+ * Generic/fallback MTU values
+ *
+ * These are taken from RFC 1122, RFC 2460, and RFC 5405.
+ * - RFC 1122, 3.3.3 defines EMTU_S ("Effective MTU for sending") and recommends
+ *   to use an EMTU_S size of of 576 bytes if the IPv4 path MTU is unknown;
+ * - RFC 2460, 5. requires a minimum IPv6 MTU of 1280 bytes;
+ * - RFC 5405, 3.2 recommends that if path MTU discovery is not done,
+ *   UDP senders should use the respective minimum values of EMTU_S.
+ */
+static inline int generic_mtu(const int af_type)
+{
+	return af_type == AF_INET6 ? 1280 : 576;
+}
+
+/** Crude approximation of IP header overhead - neglecting options. */
+static inline int estimated_header_overhead(const int af_type)
+{
+	return af_type == AF_INET6 ? 40 : 20;
+}
+
+/**
+ * Maximum transport-layer message size (MMS_S) as per RFC 1122, 3.3.3
+ * Socket must be connected.
+ */
+int generic_max_transport_msg_size(int sockfd)
+{
+	struct sockaddr_storage ss;
+	socklen_t sslen = sizeof(ss);
+	int af_type = AF_INET;
+
+	if (getpeername(sockfd, (struct sockaddr *)&ss, &sslen) < 0) {
+		PARA_ERROR_LOG("can not determine remote address type: %s\n",
+				strerror(errno));
+	} else if (!SS_IS_ADDR_V4MAPPED(&ss)) {
+		af_type = ss.ss_family;
+	}
+	return generic_mtu(af_type) - estimated_header_overhead(af_type);
+}
+
 /**
  * Print numeric host and port number (beware - uses static char).
  *
@@ -756,23 +803,36 @@ int recv_buffer(int fd, char *buf, size_t size)
  * Wrapper around the accept system call.
  *
  * \param fd The listening socket.
+ * \param rfds An optional fd_set pointer.
  * \param addr Structure which is filled in with the address of the peer socket.
  * \param size Should contain the size of the structure pointed to by \a addr.
+ * \param new_fd Result pointer.
  *
- * Accept incoming connections on \a addr. Retry if interrupted.
+ * Accept incoming connections on \a addr, retry if interrupted. If \a rfds is
+ * not \p NULL, return 0 if \a fd is not set in \a rfds without calling accept().
  *
- * \return The new file descriptor on success, negative on errors.
+ * \return Negative on errors, zero if no connections are present to be accepted,
+ * one otherwise.
  *
  * \sa accept(2).
  */
-int para_accept(int fd, void *addr, socklen_t size)
+int para_accept(int fd, fd_set *rfds, void *addr, socklen_t size, int *new_fd)
 {
-	int new_fd;
+	int ret;
 
+	if (rfds && !FD_ISSET(fd, rfds))
+		return 0;
 	do
-		new_fd = accept(fd, (struct sockaddr *) addr, &size);
-	while (new_fd < 0 && errno == EINTR);
-	return new_fd < 0? -ERRNO_TO_PARA_ERROR(errno) : new_fd;
+		ret = accept(fd, (struct sockaddr *) addr, &size);
+	while (ret < 0 && errno == EINTR);
+
+	if (ret >= 0) {
+		*new_fd = ret;
+		return 1;
+	}
+	if (errno == EAGAIN || errno == EWOULDBLOCK)
+		return 0;
+	return -ERRNO_TO_PARA_ERROR(errno);
 }
 
 /**