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DescriptionAndreas Schneider
2015-08-06 10:09:05 UTC
Description of problem:
I've tried to get nsupdate working in our Samba test environment. We use a tool called socket_wrapper [1] to build an isolated network. socket_wrapper is a library passing all socket communications through unix sockets.
socket_wrapper limits the max packet size to 1500 bytes to make it easier to write pcap files.
The function doio_send() uses sendmsg() to send the packet over the wire. nsupdate sends the tsig over a TCP connection. The packet size is 1505 bytes. socket_wrapper limits the packet size to 1500 and sends 1500 bytes, which is the return value. doio_send() detects it (see gdb output below) sets a soft error.
doio_send (sock=sock@entry=0x7ffff7f764b0, dev=0x7ffff7ed0678) at socket.c:1866
1866 if (cc < 0) {
(gdb)
1860 cc = sendmsg(sock->fd, &msghdr, 0);
(gdb) p msghdr
$6 = {msg_name = 0x0, msg_namelen = 0, msg_iov = 0x7ffff303ab70, msg_iovlen = 1, msg_control = 0x0, msg_controllen = 0, msg_flags = 0}
(gdb) n
1861 send_errno = errno;
(gdb) n
1866 if (cc < 0) {
(gdb) p cc
$7 = 1500
(gdb) n
1927 if (cc == 0) {
(gdb) n
1939 dev->n += cc;
(gdb) n
1940 if ((size_t)cc != write_count)
(gdb) p write_count
$8 = 1505
doio_send() should call sendmsg() again and just send the remaining bytes!
[1] https://cwrap.org/socket_wrapper.html
Description of problem: I've tried to get nsupdate working in our Samba test environment. We use a tool called socket_wrapper [1] to build an isolated network. socket_wrapper is a library passing all socket communications through unix sockets. socket_wrapper limits the max packet size to 1500 bytes to make it easier to write pcap files. The function doio_send() uses sendmsg() to send the packet over the wire. nsupdate sends the tsig over a TCP connection. The packet size is 1505 bytes. socket_wrapper limits the packet size to 1500 and sends 1500 bytes, which is the return value. doio_send() detects it (see gdb output below) sets a soft error. doio_send (sock=sock@entry=0x7ffff7f764b0, dev=0x7ffff7ed0678) at socket.c:1866 1866 if (cc < 0) { (gdb) 1860 cc = sendmsg(sock->fd, &msghdr, 0); (gdb) p msghdr $6 = {msg_name = 0x0, msg_namelen = 0, msg_iov = 0x7ffff303ab70, msg_iovlen = 1, msg_control = 0x0, msg_controllen = 0, msg_flags = 0} (gdb) n 1861 send_errno = errno; (gdb) n 1866 if (cc < 0) { (gdb) p cc $7 = 1500 (gdb) n 1927 if (cc == 0) { (gdb) n 1939 dev->n += cc; (gdb) n 1940 if ((size_t)cc != write_count) (gdb) p write_count $8 = 1505 doio_send() should call sendmsg() again and just send the remaining bytes! [1] https://cwrap.org/socket_wrapper.html