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As said above, when I try to SSH into my embedded system (a De0-Nano-SoC FPGA development board running Angström with Kernel 4.1) I get a "Write Failed: Broken Pipe"-Error and get disconnected. I read that this is often linked to network problems and timeouts, but in my case it's happening instantly, so it can't be a timeout-issue (can it?).

I'm searching for other solutions to this problem or other problems that might cause this error message.

Update: The other direction (SSH from embedded to host PC) works flawlessly!

Here's the output from tcpdump | grep cyclone5, juggernaut is the host PC, cyclone5 the embedded device and fritz.box is my router:

16:56:01.080879 IP6 juggernaut.fritz.box.48641 > fritz.box.domain: 3129+ A? cyclone5. (26)
16:56:01.080885 IP6 juggernaut.fritz.box.48641 > fritz.box.domain: 28063+ AAAA? cyclone5. (26)
16:56:01.082341 IP6 juggernaut.fritz.box.59915 > cyclone5.fritz.box.ssh: Flags [S], seq 1263535780, win 28640, options [mss 1432,sackOK,TS val 932516 ecr 0,nop,wscale 7], length 0
16:56:01.083400 IP6 cyclone5.fritz.box.ssh > juggernaut.fritz.box.59915: Flags [S.], seq 983702311, ack 1263535781, win 28400, options [mss 1432,sackOK,TS val 55053 ecr 932516,nop,wscale 7], length 0
16:56:01.083410 IP6 juggernaut.fritz.box.59915 > cyclone5.fritz.box.ssh: Flags [.], ack 1, win 224, options [nop,nop,TS val 932516 ecr 55053], length 0
16:56:01.083528 IP6 juggernaut.fritz.box.59915 > cyclone5.fritz.box.ssh: Flags [P.], seq 1:40, ack 1, win 224, options [nop,nop,TS val 932516 ecr 55053], length 39
16:56:01.084584 IP6 cyclone5.fritz.box.ssh > juggernaut.fritz.box.59915: Flags [.], ack 40, win 222, options [nop,nop,TS val 55053 ecr 932516], length 0
16:56:01.117746 IP6 cyclone5.fritz.box.ssh > juggernaut.fritz.box.59915: Flags [P.], seq 1:22, ack 40, win 222, options [nop,nop,TS val 55056 ecr 932516], length 21
16:56:01.117773 IP6 juggernaut.fritz.box.59915 > cyclone5.fritz.box.ssh: Flags [.], ack 22, win 224, options [nop,nop,TS val 932525 ecr 55056], length 0
16:56:01.118222 IP6 juggernaut.fritz.box.59915 > cyclone5.fritz.box.ssh: Flags [.], seq 40:1460, ack 22, win 224, options [nop,nop,TS val 932525 ecr 55056], length 1420
16:56:01.118415 IP6 juggernaut.fritz.box.59915 > cyclone5.fritz.box.ssh: Flags [P.], seq 1460:2008, ack 22, win 224, options [nop,nop,TS val 932525 ecr 55056], length 548
16:56:01.118667 IP6 cyclone5.fritz.box.ssh > juggernaut.fritz.box.59915: Flags [.], ack 2008, win 253, options [nop,nop,TS val 55056 ecr 932525], length 0
16:56:01.121526 IP6 cyclone5.fritz.box.ssh > juggernaut.fritz.box.59915: Flags [P.], seq 22:934, ack 2008, win 253, options [nop,nop,TS val 55057 ecr 932525], length 912
16:56:01.123158 IP6 juggernaut.fritz.box.59915 > cyclone5.fritz.box.ssh: Flags [P.], seq 2008:2056, ack 934, win 246, options [nop,nop,TS val 932526 ecr 55057], length 48
16:56:01.159565 IP6 cyclone5.fritz.box.ssh > juggernaut.fritz.box.59915: Flags [.], ack 2056, win 253, options [nop,nop,TS val 55061 ecr 932526], length 0
16:56:01.164976 IP6 cyclone5.fritz.box.ssh > juggernaut.fritz.box.59915: Flags [P.], seq 934:1214, ack 2056, win 253, options [nop,nop,TS val 55061 ecr 932526], length 280
16:56:01.167861 IP6 juggernaut.fritz.box.59915 > cyclone5.fritz.box.ssh: Flags [P.], seq 2056:2072, ack 1214, win 261, options [nop,nop,TS val 932538 ecr 55061], length 16
16:56:01.168671 IP6 cyclone5.fritz.box.ssh > juggernaut.fritz.box.59915: Flags [.], ack 2072, win 253, options [nop,nop,TS val 55061 ecr 932538], length 0
16:56:01.168678 IP6 juggernaut.fritz.box.59915 > cyclone5.fritz.box.ssh: Flags [P.], seq 2072:2116, ack 1214, win 261, options [nop,nop,TS val 932538 ecr 55061], length 44
16:56:01.169453 IP6 cyclone5.fritz.box.ssh > juggernaut.fritz.box.59915: Flags [.], ack 2116, win 253, options [nop,nop,TS val 55061 ecr 932538], length 0
16:56:01.169760 IP6 cyclone5.fritz.box.ssh > juggernaut.fritz.box.59915: Flags [P.], seq 1214:1258, ack 2116, win 253, options [nop,nop,TS val 55062 ecr 932538], length 44
16:56:01.169857 IP6 juggernaut.fritz.box.59915 > cyclone5.fritz.box.ssh: Flags [P.], seq 2116:2176, ack 1258, win 261, options [nop,nop,TS val 932538 ecr 55062], length 60
16:56:01.209580 IP6 cyclone5.fritz.box.ssh > juggernaut.fritz.box.59915: Flags [.], ack 2176, win 253, options [nop,nop,TS val 55066 ecr 932538], length 0
16:56:01.491968 IP6 fritz.box.domain > juggernaut.fritz.box.49687: 37977* 1/1/3 PTR cyclone5.fritz.box. (208)
16:56:03.119066 IP6 cyclone5.fritz.box.ssh > juggernaut.fritz.box.59915: Flags [P.], seq 1258:1334, ack 2176, win 253, options [nop,nop,TS val 55256 ecr 932538], length 76
16:56:03.119134 IP6 juggernaut.fritz.box.59915 > cyclone5.fritz.box.ssh: Flags [P.], seq 2176:2252, ack 1334, win 261, options [nop,nop,TS val 933025 ecr 55256], length 76
16:56:03.119954 IP6 cyclone5.fritz.box.ssh > juggernaut.fritz.box.59915: Flags [.], ack 2252, win 253, options [nop,nop,TS val 55257 ecr 933025], length 0
16:56:03.122701 IP6 cyclone5.fritz.box.ssh > juggernaut.fritz.box.59915: Flags [P.], seq 1334:1394, ack 2252, win 253, options [nop,nop,TS val 55257 ecr 933025], length 60
16:56:03.159841 IP6 juggernaut.fritz.box.59915 > cyclone5.fritz.box.ssh: Flags [.], ack 1394, win 261, options [nop,nop,TS val 933036 ecr 55257], length 0
16:56:11.034026 IP6 juggernaut.fritz.box.59915 > cyclone5.fritz.box.ssh: Flags [P.], seq 2252:2328, ack 1394, win 261, options [nop,nop,TS val 935004 ecr 55257], length 76
16:56:11.069809 IP6 cyclone5.fritz.box.ssh > juggernaut.fritz.box.59915: Flags [.], ack 2328, win 253, options [nop,nop,TS val 56052 ecr 935004], length 0
16:56:11.165970 IP6 cyclone5.fritz.box.ssh > juggernaut.fritz.box.59915: Flags [P.], seq 1394:1438, ack 2328, win 253, options [nop,nop,TS val 56061 ecr 935004], length 44
16:56:11.165983 IP6 juggernaut.fritz.box.59915 > cyclone5.fritz.box.ssh: Flags [.], ack 1438, win 261, options [nop,nop,TS val 935037 ecr 56061], length 0
16:56:11.166024 IP6 juggernaut.fritz.box.59915 > cyclone5.fritz.box.ssh: Flags [P.], seq 2328:2404, ack 1438, win 261, options [nop,nop,TS val 935037 ecr 56061], length 76
16:56:11.166816 IP6 cyclone5.fritz.box.ssh > juggernaut.fritz.box.59915: Flags [.], ack 2404, win 253, options [nop,nop,TS val 56061 ecr 935037], length 0
16:56:11.167921 IP6 cyclone5.fritz.box.ssh > juggernaut.fritz.box.59915: Flags [P.], seq 1438:1466, ack 2404, win 253, options [nop,nop,TS val 56061 ecr 935037], length 28
16:56:11.167985 IP6 juggernaut.fritz.box.59915 > cyclone5.fritz.box.ssh: Flags [P.], seq 2404:2508, ack 1466, win 261, options [nop,nop,TS val 935038 ecr 56061], length 104
16:56:11.173648 IP6 cyclone5.fritz.box.ssh > juggernaut.fritz.box.59915: Flags [R.], seq 1466, ack 2508, win 253, options [nop,nop,TS val 0 ecr 935038], length 0
  • What does tcpdump show happening? – thrig Apr 19 '16 at 14:49
  • Can you give us the solution that you already have for this issue ( since you are searching for other solutions ), by providing it as an answer? That might prevent unnecessary duplicate effort. – Anthon Apr 19 '16 at 14:51
  • @thrig I'm working through that now. – TheBrillowable Apr 19 '16 at 14:52
  • @Anthon other solutions aren't working in this case, those would include increasing the Server/ClientAliveInterval times in the sshd_config as stated in other similar questions – TheBrillowable Apr 19 '16 at 14:53
  • @thrig I added the tcpdump output to the original question, can't make a lot of it though. – TheBrillowable Apr 19 '16 at 14:59
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I think your issue is network related 99% but, just to consider 1%... Is your OS running on flash memory?

I had similar issues when working on usb and sdcard based installations. Sometimes system got unstable, remounted RO and one of first symptoms was unsuccesful ssh connection, with same error output. When i had the luck to keep an alive existing ssh session i could almost normally work on my box, including sshing other servers.

  • The system is running on a sdcard, yeah. I don't think it is network-related since the other direction works without problems. Do you know of any fixes for flash-based systems? – TheBrillowable Apr 19 '16 at 15:35
  • I actually went ramdisk. If you have tiny installation and enough ram give it a try. But first check if this is your problem, when it happens you should have an unresponsive system soon. – realpclaudio Apr 19 '16 at 15:41

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