> > On Wed, Jan 25, 2017 at 12:23:35PM -0500, Frediano Ziglio wrote: > > > > > > When used with QEMU at least, both SPICE and VNC live in the same port > > > range (5900+). It is thus not entirely uncommon for a user to mistakenly > > > connect to a SPICE server with a VNC client, or vica-verca. > > > > > > When connecting to VNC server with a SPICE client, you quickly get an > > > error. This is because the VNC server sends its short greeting and then > > > sees the RedLinkMess from the SPICE client, realizes its garbage and > > > drops the connection. > > > > > > When connecting to a SPICE server with a VNC client though, you get an > > > indefinite hang. The VNC client is waiting for the VNC greeting, which > > > the SPICE server will never send. The SPICE server is waiting for the > > > RedLinkMess which the VNC client will never send. > > > > > > Since VNC is a server sends first protocol and SPICE is a client sends > > > first protocol, it would seem this problem is impossible to fix, but > > > I think it is possible to tweak things so it can be more gracefully > > > handled. > > > > > > In VNC the protocol starts with the follow data sent: > > > > > > Server: "RFB 003.008\n" > > > Client: "RFB 003.008\n" > > > > > > What I'm thinking is that we could easily change the VNC client so that > > > it will send some bytes first. eg > > > > > > Client: "RFB " > > > Server: "RFB 003.008\n" > > > Client: "003.008\n" > > > > > > From the VNC server POV, it'll still be receiving the same 12 bytes from > > > the client - it just happens that 4 of them might arrive a tiny bit > > > earlier than the other 8 of them. IOW nothing should break in the VNC > > > server from this change. > > > > > > I tried this, but we still get a hang in the SPICE server. The problem > > > is that the SPICE server code is waiting for the full RedLinkMess > > > message to be received before checking its content. > > > > > > Can we change the SPICE server so that it reads the 'uint32 magic' first, > > > validates that, and then reads the remainder of RedLinkMess ? > > > > > > This would solve the problem, as the SPICE server would see 'RFB ' as the > > > magic, realize it was garbage and so close the connection. The VNC client > > > which is waiting for the VNC greeting will thus terminate rather than > > > hanging > > > forever. > > > > > > Regards, > > > Daniel > > > > Perhaps another solution would be to add a timeout to spice server so > > after, say, 2/3 seconds it would close the connection. > > > > This would work even without changing the VNC client. > > I'm not a fan of timeouts because this could negatively impact on > genuine spice clients which hit a latency spike on the network > for whatever reason. The incremental read of RedLinkMess by constrast > is guaranteed to not have any chance of negative impact on spice clients. > > Regards, > Daniel
So you would like something like that: diff --git a/server/reds.c b/server/reds.c index 8db70ee..50098df 100644 --- a/server/reds.c +++ b/server/reds.c @@ -2264,12 +2264,6 @@ static void reds_handle_read_header_done(void *opaque) header->minor_version = GUINT32_FROM_LE(header->minor_version); header->size = GUINT32_FROM_LE(header->size); - if (header->magic != SPICE_MAGIC) { - reds_send_link_error(link, SPICE_LINK_ERR_INVALID_MAGIC); - reds_link_free(link); - return; - } - if (header->major_version != SPICE_VERSION_MAJOR) { if (header->major_version > 0) { reds_send_link_error(link, SPICE_LINK_ERR_VERSION_MISMATCH); @@ -2296,13 +2290,31 @@ static void reds_handle_read_header_done(void *opaque) link); } +static void reds_handle_read_magic_done(void *opaque) +{ + RedLinkInfo *link = (RedLinkInfo *)opaque; + const SpiceLinkHeader *header = &link->link_header; + + if (header->magic != SPICE_MAGIC) { + reds_send_link_error(link, SPICE_LINK_ERR_INVALID_MAGIC); + reds_link_free(link); + return; + } + + reds_stream_async_read(link->stream, + ((uint8_t *)&link->link_header) + sizeof(header->magic), + sizeof(SpiceLinkHeader) - sizeof(header->magic), + reds_handle_read_header_done, + link); +} + static void reds_handle_new_link(RedLinkInfo *link) { reds_stream_set_async_error_handler(link->stream, reds_handle_link_error); reds_stream_async_read(link->stream, (uint8_t *)&link->link_header, - sizeof(SpiceLinkHeader), - reds_handle_read_header_done, + sizeof(link->link_header.magic), + reds_handle_read_magic_done, link); } ? I don't think the extra code execute is much of a problem. Frediano _______________________________________________ Spice-devel mailing list Spice-devel@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/spice-devel