telnet hangs after certain symbol typed
Posted: Wed Oct 07, 2020 7:53 am
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:
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?
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])
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?