Handle EMSGSIZE on UNIX domain sockets.

On some systems (eg, FreeBSD) the default SO_SNDBUF for UNIX
domain sockets is to small, and EMSGSIZE is returned. Other
systems provide a larger default send buffer, but there is
still no guarantee that the buffer will be sized appropriately.

This patch modifies the sendto() path to attempt to resize
the SO_SNDBUF dynamically upon an EMSGSIZE failure, and then
retry the send.

This fixes local DCE/RPC errors on FreeBSD, eg:

https://lists.samba.org/archive/samba-technical/2013-January/089881.html

Signed-Off-By: Landon Fuller <landonf@bikemonkey.org>

Reviewed-by: Andrew Bartlett <abartlet@samba.org>

Autobuild-User(master): Andrew Bartlett <abartlet@samba.org>
Autobuild-Date(master): Sat Mar  2 23:34:03 CET 2013 on sn-devel-104

1 files changed, 26 insertions, 9 deletions

diff --git a/source4/lib/socket/socket_unix.c b/source4/lib/socket/socket_unix.c
index 4755e796a4a..049e5707c87 100644
--- a/source4/lib/socket/socket_unix.c
+++ b/source4/lib/socket/socket_unix.c
@@ -263,26 +263,43 @@ static NTSTATUS unixdom_sendto(struct socket_context *sock,
 			       const DATA_BLOB *blob, size_t *sendlen, 
 			       const struct socket_address *dest)
 {
+	struct sockaddr_un srv_addr;
+	const struct sockaddr *sa;
+	socklen_t sa_len;
 	ssize_t len;
+
 	*sendlen = 0;
-		
+
 	if (dest->sockaddr) {
-		len = sendto(sock->fd, blob->data, blob->length, 0, 
-			     dest->sockaddr, dest->sockaddrlen);
+		sa = dest->sockaddr;
+		sa_len = dest->sockaddrlen;
 	} else {
-		struct sockaddr_un srv_addr;
-		
 		if (strlen(dest->addr)+1 > sizeof(srv_addr.sun_path)) {
 			return NT_STATUS_OBJECT_PATH_INVALID;
 		}
-		
+
 		ZERO_STRUCT(srv_addr);
 		srv_addr.sun_family = AF_UNIX;
-		snprintf(srv_addr.sun_path, sizeof(srv_addr.sun_path), "%s", dest->addr);
+		snprintf(srv_addr.sun_path, sizeof(srv_addr.sun_path), "%s",
+			 dest->addr);
+		sa = (struct sockaddr *) &srv_addr;
+		sa_len = sizeof(srv_addr);
+	}
+
+	len = sendto(sock->fd, blob->data, blob->length, 0, sa, sa_len);
 
-		len = sendto(sock->fd, blob->data, blob->length, 0, 
-			     (struct sockaddr *)&srv_addr, sizeof(srv_addr));
+	/* retry once */
+	if (len == -1 && errno == EMSGSIZE) {
+		/* round up in 1K increments */
+		int bufsize = ((blob->length + 1023) & (~1023));
+		if (setsockopt(sock->fd, SOL_SOCKET, SO_SNDBUF, &bufsize,
+			       sizeof(bufsize)) == -1)
+		{
+			return map_nt_error_from_unix_common(errno);
+		}
+		len = sendto(sock->fd, blob->data, blob->length, 0, sa, sa_len);
 	}
+
 	if (len == -1) {
 		return map_nt_error_from_unix_common(errno);
 	}