telnet hangs after certain symbol typed

[romzhke]

Hello colleagues.
Couple of days ago i have encountered behaviour i cannot explain. I run Cisco IOL images and using telnet to connect to the console. So the thing is that when i type exactly 'd' letter (for example i type "no ip domain lookup"), the telnet session hags totally. the only way to make it working back is to reconnect.
I have tried to look what's happening inside iol_wrapper, so i've used "strace" tool to attach to the telnet session process and i totally do not see any issue with the "d" letter:

Code: Select all

wait4(-1, 0x7ffdaed7b5c4, WNOHANG|WSTOPPED, NULL) = 0
select(1024, [5 6 7 8 10 12 14 16 17 18], NULL, NULL, NULL) = 1 (in [5])
read(5, "e", 1)                         = 1
sendto(16, "e", 1, 0, NULL, 0)          = 1
sendto(17, "e", 1, 0, NULL, 0)          = 1
sendto(18, "e", 1, 0, NULL, 0)          = 1
wait4(-1, 0x7ffdaed7b5c4, WNOHANG|WSTOPPED, NULL) = 0
select(1024, [5 6 7 8 10 12 14 16 17 18], NULL, NULL, NULL) = 1 (in [18])
recvfrom(18, "n", 1, 0, NULL, NULL)     = 1
write(4, "n", 1)                        = 1
wait4(-1, 0x7ffdaed7b5c4, WNOHANG|WSTOPPED, NULL) = 0
select(1024, [5 6 7 8 10 12 14 16 17 18], NULL, NULL, NULL) = 1 (in [5])
read(5, "n", 1)                         = 1
sendto(16, "n", 1, 0, NULL, 0)          = 1
sendto(17, "n", 1, 0, NULL, 0)          = 1
sendto(18, "n", 1, 0, NULL, 0)          = 1
wait4(-1, 0x7ffdaed7b5c4, WNOHANG|WSTOPPED, NULL) = 0
select(1024, [5 6 7 8 10 12 14 16 17 18], NULL, NULL, NULL) = 1 (in [18])
recvfrom(18, "d", 1, 0, NULL, NULL)     = 1
write(4, "d", 1)                        = 1
wait4(-1, 0x7ffdaed7b5c4, WNOHANG|WSTOPPED, NULL) = 0
select(1024, [5 6 7 8 10 12 14 16 17 18], NULL, NULL, NULL) = 1 (in [5])
read(5, "d", 1)                         = 1
sendto(16, "d", 1, 0, NULL, 0)          = 1
sendto(17, "d", 1, 0, NULL, 0)          = 1
sendto(18, "d", 1, 0, NULL, 0)          = 1
wait4(-1, 0x7ffdaed7b5c4, WNOHANG|WSTOPPED, NULL) = 0
select(1024, [5 6 7 8 10 12 14 16 17 18], NULL, NULL, NULL) = 1 (in [6])
read(6, "\2\1\0\20\0\0\1\0\1\200\302\0\0\0\252\273\314\0\20\0\0&BB\3\0\0\0\0\0\200\1"..., 10000) = 68
write(8, "\1\200\302\0\0\0\252\273\314\0\20\0\0&BB\3\0\0\0\0\0\200\1\252\273\314\0\20\0\0\0"..., 60) = 60
wait4(-1, 0x7ffdaed7b5c4, WNOHANG|WSTOPPED, NULL) = 0
select(1024, [5 6 7 8 10 12 14 16 17 18], NULL, NULL, NULL) = 1 (in [6])

What i have tried also. I have updated the eve ng to the latest version. Does not help.
I have asked colleagues to try to telnet from their desktop to make sure it is not my host issue, so they have the same behaviour. So it is definitely the server side issue, But i have no idea what is happening. Any thoughts?

[Uldis (UD)]

console hangs on very bad IOL image 15.5.2T, avoid use it.
Better 15.4.2T

[romzhke]

Hi, i am using several images, but none of them with the mentioned version. Also to mention, i have used the same images, i have troubles with now, several months and there weren't any issues. I'm confused.
to be precise about images, the list is:
L3-ADVENTERPRISEK9-M-15.2-M5.3.bin
L3-ADVENTERPRISEK9-M-15.2-S7.bin
i86bi_linux_l2-adventerprisek9-ms.SSA.high_iron_20180510.bin
i86bi_linux_l2-advipservicesk9-ms.high_iron_20170202.bin
i86bi_linux_l2-ipbasek9-ms.high_iron_aug9_2017b.bin

[Uldis (UD)]

no idea mate, but I dont face such issues

[romzhke]

So i did not figure out what was it. but o have rebooted be ESXi hypervisor, where Eve is spinning and it seems this has helped. i can not work over telnet as usual.