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| 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/server.c | |
| parent | 75368aab9ba27f762acf5a51062c951a1fb1e006 (diff) | |
| download | qemu-c203c59ad9dc677b27e00ba76d221fd7e93c1aa6.zip qemu-c203c59ad9dc677b27e00ba76d221fd7e93c1aa6.tar.gz qemu-c203c59ad9dc677b27e00ba76d221fd7e93c1aa6.tar.bz2 | |
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/server.c')
| -rw-r--r-- | nbd/server.c | 15 |
1 files changed, 11 insertions, 4 deletions
diff --git a/nbd/server.c b/nbd/server.c index fa01e49..afc1ec4 100644 --- a/nbd/server.c +++ b/nbd/server.c @@ -81,6 +81,7 @@ struct NBDClient { int refcount; void (*close)(NBDClient *client); + bool no_zeroes; NBDExport *exp; QCryptoTLSCreds *tlscreds; char *tlsaclname; @@ -450,6 +451,11 @@ static int nbd_negotiate_options(NBDClient *client) fixedNewstyle = true; flags &= ~NBD_FLAG_C_FIXED_NEWSTYLE; } + if (flags & NBD_FLAG_C_NO_ZEROES) { + TRACE("Client supports no zeroes at handshake end"); + client->no_zeroes = true; + flags &= ~NBD_FLAG_C_NO_ZEROES; + } if (flags != 0) { TRACE("Unknown client flags 0x%" PRIx32 " received", flags); return -EIO; @@ -602,6 +608,7 @@ static coroutine_fn int nbd_negotiate(NBDClientNewData *data) const uint16_t myflags = (NBD_FLAG_HAS_FLAGS | NBD_FLAG_SEND_TRIM | NBD_FLAG_SEND_FLUSH | NBD_FLAG_SEND_FUA); bool oldStyle; + size_t len; /* Old style negotiation header without options [ 0 .. 7] passwd ("NBDMAGIC") @@ -618,7 +625,7 @@ static coroutine_fn int nbd_negotiate(NBDClientNewData *data) ....options sent.... [18 .. 25] size [26 .. 27] export flags - [28 .. 151] reserved (0) + [28 .. 151] reserved (0, omit if no_zeroes) */ qio_channel_set_blocking(client->ioc, false, NULL); @@ -637,7 +644,7 @@ static coroutine_fn int nbd_negotiate(NBDClientNewData *data) stw_be_p(buf + 26, client->exp->nbdflags | myflags); } else { stq_be_p(buf + 8, NBD_OPTS_MAGIC); - stw_be_p(buf + 16, NBD_FLAG_FIXED_NEWSTYLE); + stw_be_p(buf + 16, NBD_FLAG_FIXED_NEWSTYLE | NBD_FLAG_NO_ZEROES); } if (oldStyle) { @@ -664,8 +671,8 @@ static coroutine_fn int nbd_negotiate(NBDClientNewData *data) client->exp->size, client->exp->nbdflags | myflags); stq_be_p(buf + 18, client->exp->size); stw_be_p(buf + 26, client->exp->nbdflags | myflags); - if (nbd_negotiate_write(client->ioc, buf + 18, sizeof(buf) - 18) != - sizeof(buf) - 18) { + len = client->no_zeroes ? 10 : sizeof(buf) - 18; + if (nbd_negotiate_write(client->ioc, buf + 18, len) != len) { LOG("write failed"); goto fail; } |