diff options
| author | Eric Blake <eblake@redhat.com> | 2016-10-14 13:33:14 -0500 |
|---|---|---|
| committer | Paolo Bonzini <pbonzini@redhat.com> | 2016-11-02 09:28:56 +0100 |
| commit | c203c59ad9dc677b27e00ba76d221fd7e93c1aa6 (patch) | |
| tree | 8d19b580c4128be92df039034cf12ea50068fc31 /nbd/client.c | |
| parent | 75368aab9ba27f762acf5a51062c951a1fb1e006 (diff) | |
| download | qemu-c203c59ad9dc677b27e00ba76d221fd7e93c1aa6.tar.gz | |
nbd: Support shorter handshake
The NBD Protocol allows the server and client to mutually agree
on a shorter handshake (omit the 124 bytes of reserved 0), via
the server advertising NBD_FLAG_NO_ZEROES and the client
acknowledging with NBD_FLAG_C_NO_ZEROES (only possible in
newstyle, whether or not it is fixed newstyle). It doesn't
shave much off the wire, but we might as well implement it.
Signed-off-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Alex Bligh <alex@alex.org.uk>
Message-Id: <1476469998-28592-13-git-send-email-eblake@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Diffstat (limited to 'nbd/client.c')
| -rw-r--r-- | nbd/client.c | 8 |
1 files changed, 7 insertions, 1 deletions
diff --git a/nbd/client.c b/nbd/client.c index 0afb8be15d..b29963b942 100644 --- a/nbd/client.c +++ b/nbd/client.c @@ -440,6 +440,7 @@ int nbd_receive_negotiate(QIOChannel *ioc, const char *name, uint16_t *flags, char buf[256]; uint64_t magic, s; int rc; + bool zeroes = true; TRACE("Receiving negotiation tlscreds=%p hostname=%s.", tlscreds, hostname ? hostname : "<null>"); @@ -504,6 +505,11 @@ int nbd_receive_negotiate(QIOChannel *ioc, const char *name, uint16_t *flags, TRACE("Server supports fixed new style"); clientflags |= NBD_FLAG_C_FIXED_NEWSTYLE; } + if (globalflags & NBD_FLAG_NO_ZEROES) { + zeroes = false; + TRACE("Server supports no zeroes"); + clientflags |= NBD_FLAG_C_NO_ZEROES; + } /* client requested flags */ clientflags = cpu_to_be32(clientflags); if (write_sync(ioc, &clientflags, sizeof(clientflags)) != @@ -591,7 +597,7 @@ int nbd_receive_negotiate(QIOChannel *ioc, const char *name, uint16_t *flags, } TRACE("Size is %" PRIu64 ", export flags %" PRIx16, *size, *flags); - if (drop_sync(ioc, 124) != 124) { + if (zeroes && drop_sync(ioc, 124) != 124) { error_setg(errp, "Failed to read reserved block"); goto fail; } |