| Message ID | 1460153158-21612-12-git-send-email-eblake@redhat.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On 8 Apr 2016, at 23:05, Eric Blake <eblake@redhat.com> wrote: > The server has a nice helper function nbd_negotiate_drop_sync() > which lets it easily ignore fluff from the client (such as the > payload to an unknown option request). We can't quite make it > common, since it depends on nbd_negotiate_read() which handles > coroutine magic, but we can copy the idea into the client where > we have places where we want to ignore data (such as the > description tacked on the end of NBD_REP_SERVER). > > Signed-off-by: Eric Blake <eblake@redhat.com> Reviewed-by: Alex Bligh <alex@alex.org.uk> > --- > nbd/client.c | 45 ++++++++++++++++++++++++++++++++------------- > 1 file changed, 32 insertions(+), 13 deletions(-) > > diff --git a/nbd/client.c b/nbd/client.c > index 07b8d2e..b2dfc11 100644 > --- a/nbd/client.c > +++ b/nbd/client.c > @@ -75,6 +75,32 @@ static QTAILQ_HEAD(, NBDExport) exports = QTAILQ_HEAD_INITIALIZER(exports); > > */ > > +/* Discard length bytes from channel. Return -errno on failure, or > + * the amount of bytes consumed. */ > +static ssize_t drop_sync(QIOChannel *ioc, size_t size) > +{ > + ssize_t ret, dropped = size; > + char small[1024]; > + char *buffer; > + > + buffer = sizeof(small) < size ? small : g_malloc(MIN(65536, size)); > + while (size > 0) { > + ret = read_sync(ioc, buffer, MIN(65536, size)); > + if (ret < 0) { > + goto cleanup; > + } > + assert(ret <= size); > + size -= ret; > + } > + ret = dropped; > + > + cleanup: > + if (buffer != small) { > + g_free(buffer); > + } > + return ret; > +} > + > /* Send an option request. Return 0 if successful, -1 with errp set if > * it is impossible to continue. */ > static int nbd_send_option_request(QIOChannel *ioc, uint32_t opt, > @@ -255,18 +281,11 @@ static int nbd_receive_list(QIOChannel *ioc, char **name, Error **errp) > } > (*name)[namelen] = '\0'; > len -= namelen; > - if (len) { > - char *buf = g_malloc(len + 1); > - if (read_sync(ioc, buf, len) != len) { > - error_setg(errp, "failed to read export description"); > - g_free(*name); > - g_free(buf); > - *name = NULL; > - return -1; > - } > - buf[len] = '\0'; > - TRACE("Ignoring export description: %s", buf); > - g_free(buf); > + if (drop_sync(ioc, len) != len) { > + error_setg(errp, "failed to read export description"); > + g_free(*name); > + *name = NULL; > + return -1; > } > } else { > error_setg(errp, "Unexpected reply type %" PRIx32 " expected %x", > @@ -539,7 +558,7 @@ int nbd_receive_negotiate(QIOChannel *ioc, const char *name, uint32_t *flags, > goto fail; > } > > - if (read_sync(ioc, &buf, 124) != 124) { > + if (drop_sync(ioc, 124) != 124) { > error_setg(errp, "Failed to read reserved block"); > goto fail; > } > -- > 2.5.5 > >
diff --git a/nbd/client.c b/nbd/client.c index 07b8d2e..b2dfc11 100644 --- a/nbd/client.c +++ b/nbd/client.c @@ -75,6 +75,32 @@ static QTAILQ_HEAD(, NBDExport) exports = QTAILQ_HEAD_INITIALIZER(exports); */ +/* Discard length bytes from channel. Return -errno on failure, or + * the amount of bytes consumed. */ +static ssize_t drop_sync(QIOChannel *ioc, size_t size) +{ + ssize_t ret, dropped = size; + char small[1024]; + char *buffer; + + buffer = sizeof(small) < size ? small : g_malloc(MIN(65536, size)); + while (size > 0) { + ret = read_sync(ioc, buffer, MIN(65536, size)); + if (ret < 0) { + goto cleanup; + } + assert(ret <= size); + size -= ret; + } + ret = dropped; + + cleanup: + if (buffer != small) { + g_free(buffer); + } + return ret; +} + /* Send an option request. Return 0 if successful, -1 with errp set if * it is impossible to continue. */ static int nbd_send_option_request(QIOChannel *ioc, uint32_t opt, @@ -255,18 +281,11 @@ static int nbd_receive_list(QIOChannel *ioc, char **name, Error **errp) } (*name)[namelen] = '\0'; len -= namelen; - if (len) { - char *buf = g_malloc(len + 1); - if (read_sync(ioc, buf, len) != len) { - error_setg(errp, "failed to read export description"); - g_free(*name); - g_free(buf); - *name = NULL; - return -1; - } - buf[len] = '\0'; - TRACE("Ignoring export description: %s", buf); - g_free(buf); + if (drop_sync(ioc, len) != len) { + error_setg(errp, "failed to read export description"); + g_free(*name); + *name = NULL; + return -1; } } else { error_setg(errp, "Unexpected reply type %" PRIx32 " expected %x", @@ -539,7 +558,7 @@ int nbd_receive_negotiate(QIOChannel *ioc, const char *name, uint32_t *flags, goto fail; } - if (read_sync(ioc, &buf, 124) != 124) { + if (drop_sync(ioc, 124) != 124) { error_setg(errp, "Failed to read reserved block"); goto fail; }
The server has a nice helper function nbd_negotiate_drop_sync() which lets it easily ignore fluff from the client (such as the payload to an unknown option request). We can't quite make it common, since it depends on nbd_negotiate_read() which handles coroutine magic, but we can copy the idea into the client where we have places where we want to ignore data (such as the description tacked on the end of NBD_REP_SERVER). Signed-off-by: Eric Blake <eblake@redhat.com> --- nbd/client.c | 45 ++++++++++++++++++++++++++++++++------------- 1 file changed, 32 insertions(+), 13 deletions(-)