nbd-server passes flags in 2 octets.
smallflags = (uint16_t)(flags & ~((uint16_t)0));
smallflags = htons(smallflags);
if (write(client->net, &smallflags, sizeof(smallflags)) <
0) {
err("Negotiation failed: %m");
That takes the least significant two bytes of flags, converts to
network order, and writes to the net.
nbd-client reads these in negotiate() as follows:
void negotiate(int sock, u64 *rsize64, u32 *flags, char* name) {
...
if(name) {
...
*flags = ((u32)ntohs(tmp)) << 16;
...
}
...
if(!name) {
if (read(sock, flags, sizeof(*flags)) < 0)
err("Failed/4: %m\n");
*flags = ntohl(*flags);
} ...
The first assignment (line 153) converts back to host order and
puts the flags in the top 2 bytes (host order) of flags (<<16).
However, line 215 does
int read_only = (flags & NBD_FLAG_READ_ONLY) ? 1 : 0;
NBD_FLAG_READ_ONLY is 1<<0, which means this can never be set
if the first evaluation (line 215) is done.
I think the "<< 16" on line 215 is superfluous. The flags should
simply be converted to host order, and assigned to "flags", so
they will live in least significant two bytes (where they came
from).
--
Alex Bligh
------------------------------------------------------------------------------
Achieve unprecedented app performance and reliability
What every C/C++ and Fortran developer should know.
Learn how Intel has extended the reach of its next-generation tools
to help boost performance applications - inlcuding clusters.
http://p.sf.net/sfu/intel-dev2devmay
_______________________________________________
Nbd-general mailing list
[email protected]
https://lists.sourceforge.net/lists/listinfo/nbd-general
