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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [MirageOS-devel] More troubles with tcp on ARM
On 10 April 2015 at 05:29, Magnus Therning <magnus@xxxxxxxxxxxx> wrote: > On Thu, Apr 09, 2015 at 10:18:53PM +0200, Magnus Therning wrote: > [...] > >> >> It works fine in Unix mode, both on x86 and on my cubietruck board. >> When built in Xen mode though it doesn't work as well. >> >> When run in Unix mode I see the expected behaviour: >> >> shell my server console >> ----- ----------------- >> % echo hello | ncat -4 -u localhost 18081 -> udp: 127.0.0.1:46507 >> udp: 6 - hello >> >> % echo hello | ncat -4 localhost 18080 -> tcp: 127.0.0.1:59888 >> hello 6 - hello >> >> % echo foobar | ncat -4 localhost 18080 -> tcp: 127.0.0.1:59888 >> foobar 6 - foobar > > That last line should of course read > > foobar 7 - foobar > > That was caused by a copy-paste mistake of mine. > >> When running the server in a VM on ARM I see the same behaviour for >> UDP, but for TCP it changes. >> >> shell my server console >> ----- ----------------- >> % echo hello | ncat -4 -u localhost 18081 -> udp: 127.0.0.1:46507 >> udp: 6 - hello >> >> % echo hello | ncat -4 localhost 18080 -> tcp: 127.0.0.1:59888 >> 6 - >> 6 - > > And here there are even more copy-paste mistakes. I must have been > tired yesterday. Just disregard the `localhost` and `127.0.0.1`, that > should of course be the IPs of my cubietruck and my PC, respectively. > > I did a little bit more testing of this just now, and found something > surprising. This is against a VM on ARM: > > ~~~ > % echo thisisalongerstring | ncat -4 192.168.0.33 18080 > alongerstring > > -> > > tcp: 192.168.0.11:48731 > 6 - > 14 - alongerstring > ~~~ > > and > > ~~~ > % echo thisisalongerstringandthisislongerstill | ncat -4 192.168.0.33 18080 > alongerstringandthisislongerstill > > -> > > tcp: 192.168.0.11:48732 > 6 - > 34 - alongerstringandthisislongerstill > ~~~ > > and if I send a string that is shorter than 6 characters (I'm guessing > including the trailing \r\n), then `ncat` hangs and on the ARM I only > see a single line of "length - content": > > ~~~ > tcp: 192.168.0.11:48766 > 6 - > ~~~ > > I do wonder where those initial 6 characters go... Interesting! Probably the easiest thing now is to git clone mirage-net-xen and/or mirage-tcpip and add some code to dump out the buffer at various points: https://github.com/mirage/mirage-net-xen/ https://github.com/mirage/mirage-tcpip/ (use e.g. "opam pin add tcpip mirage-tcpip" to rebuild with your debug version, then make clean and rebuild your unikernel) I think this is the first point where we learn that Xen has placed the new packet in our buffer: https://github.com/mirage/mirage-net-xen/blob/541e86f53cb8cf426aabdd7f090779fc5ea9fe93/lib/netif.ml#L387 A few Cstruct.hexdump calls along the way should let you see where it first differs from the wireshare capture (assuming that looks OK). -- Dr Thomas Leonard http://0install.net/ GPG: 9242 9807 C985 3C07 44A6 8B9A AE07 8280 59A5 3CC1 GPG: DA98 25AE CAD0 8975 7CDA BD8E 0713 3F96 CA74 D8BA _______________________________________________ MirageOS-devel mailing list MirageOS-devel@xxxxxxxxxxxxxxxxxxxx http://lists.xenproject.org/cgi-bin/mailman/listinfo/mirageos-devel
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