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SubjectNCSA telnet doesn't work any more

I have already posted this in linux-net, but got no single response. Now
I have some more data, so I'm posting this once more.


I have found that linux 1.3.74 and 1.3.77 does not work with NCSA telnet for
DOS (or rather NCSA telnet doesn't with linux). From NCSA side it looks like
the conection is open, but nothing (even login's output) arrives. From the
linux side in.telnetd is launched, but nothing more.

netstat -o:

Active Internet connections
Proto Recv-Q Send-Q Local Address Foreign Address (State)
User
tcp -1 24 jacka:telnet lenki:12115 ESTABLISHED
root on (32.95/10)
Active UNIX domain sockets
Proto RefCnt Flags Type State Path
unix 2 [ ] SOCK_STREAM UNCONNECTED /dev/log
unix 2 [ ] SOCK_STREAM UNCONNECTED /dev/log

tcpdump -v:

18:08:10.000000 1.2.3.88.11134 > kakofonix.posnet.com.telnet: S 37216256:37216256(0) win 1024 <mss 1500> (ttl 100, id 1)
18:08:10.000000 kakofonix.posnet.com.telnet > 1.2.3.88.11134: S 3949214610:3949214610(0) ack 37216257 win 13140 <mss 1460> (ttl 64, id 1692)
18:08:10.000000 1.2.3.88.11134 > kakofonix.posnet.com.telnet: P 1:16(15) ack 1 win 1024 (ttl 100, id 2)
18:08:10.000000 kakofonix.posnet.com.telnet > 1.2.3.88.11134: P 1:4(3) ack 16 win 13125 (DF) (ttl 64, id 1695)
18:08:11.000000 kakofonix.posnet.com.telnet > 1.2.3.88.11134: P 1:4(3) ack 16 win 13125 (DF) (ttl 64, id 1696)
18:08:11.000000 kakofonix.posnet.com.telnet > 1.2.3.88.11134: P 1:4(3) ack 16 win 13125 (DF) (ttl 64, id 1697)
18:08:12.000000 kakofonix.posnet.com.telnet > 1.2.3.88.11134: P 1:4(3) ack 16 win 13125 (DF) (ttl 64, id 1698)
18:08:12.000000 1.2.3.88.11134 > kakofonix.posnet.com.telnet: P 1:16(15) ack 1 win 1024 (ttl 100, id 3)
18:08:12.000000 kakofonix.posnet.com.telnet > 1.2.3.88.11134: . ack 16 win 13125 (ttl 64, id 1699)
18:08:12.000000 1.2.3.88.11134 > kakofonix.posnet.com.telnet: . ack 1 win 1024 (ttl 100, id 4)
18:08:12.000000 kakofonix.posnet.com.telnet > 1.2.3.88.11134: . ack 16 win 13125 (ttl 64, id 1700)
18:08:12.000000 1.2.3.88.11134 > kakofonix.posnet.com.telnet: . ack 1 win 1024 (ttl 100, id 5)
18:08:13.000000 kakofonix.posnet.com.telnet > 1.2.3.88.11134: P 1:4(3) ack 16 win 13125 (DF) (ttl 64, id 1701)
18:08:17.000000 kakofonix.posnet.com.telnet > 1.2.3.88.11134: P 1:4(3) ack 16 win 13125 (DF) (ttl 64, id 1702)
18:08:23.000000 kakofonix.posnet.com.telnet > 1.2.3.88.11134: P 1:4(3) ack 16 win 13125 (DF) (ttl 64, id 1703)
18:08:36.000000 kakofonix.posnet.com.telnet > 1.2.3.88.11134: P 1:4(3) ack 16 win 13125 (DF) (ttl 64, id 1704)
...........


1.2.3.88 is a dos machine running NCSA telnet 2.3.07 on a packet driver
kakofonix is a linux machine

both on a local network

With linux 1.2.13 it looks like:

18:11:19.000000 1.2.3.88.14570 > kakofonix.posnet.com.telnet: S 51290112:51290112(0) win 1024 <mss 1500> (ttl 100, id 1)
18:11:19.000000 kakofonix.posnet.com.telnet > 1.2.3.88.14570: S 4137851704:4137851704(0) ack 51290113 win 14335 <mss 1436> (ttl 64, id 175)
18:11:19.000000 1.2.3.88.14570 > kakofonix.posnet.com.telnet: P 1:16(15) ack 1 win 1024 (ttl 100, id 2)
18:11:19.000000 kakofonix.posnet.com.telnet > 1.2.3.88.14570: . ack 16 win 14320 (ttl 64, id 176)
18:11:19.000000 kakofonix.posnet.com.telnet > 1.2.3.88.14570: P 1:4(3) ack 16 win 14320 (ttl 64, id 179)
18:11:19.000000 1.2.3.88.14570 > kakofonix.posnet.com.telnet: P 16:19(3) ack 4 win 1024 (ttl 100, id 3)
18:11:19.000000 kakofonix.posnet.com.telnet > 1.2.3.88.14570: . ack 19 win 14317 (ttl 64, id 180)
18:11:20.000000 kakofonix.posnet.com.telnet > 1.2.3.88.14570: P 4:25(21) ack 19 win 14317 (ttl 64, id 181)
18:11:20.000000 1.2.3.88.14570 > kakofonix.posnet.com.telnet: P 19:46(27) ack 25 win 1024 (ttl 100, id 4)
18:11:20.000000 kakofonix.posnet.com.telnet > 1.2.3.88.14570: . ack 46 win 14290 (ttl 64, id 182)
18:11:20.000000 kakofonix.posnet.com.telnet > 1.2.3.88.14570: P 25:31(6) ack 46 win 14335 (ttl 64, id 183)
18:11:20.000000 1.2.3.88.14570 > kakofonix.posnet.com.telnet: P 46:57(11) ack 31 win 1024 (ttl 100, id 5)
18:11:20.000000 kakofonix.posnet.com.telnet > 1.2.3.88.14570: . ack 57 win 14324 (ttl 64, id 184)
18:11:20.000000 kakofonix.posnet.com.telnet > 1.2.3.88.14570: P 31:40(9) ack 57 win 14335 (ttl 64, id 185)
18:11:20.000000 1.2.3.88.14570 > kakofonix.posnet.com.telnet: P 57:66(9) ack 40 win 1024 (ttl 100, id 6)
18:11:20.000000 kakofonix.posnet.com.telnet > 1.2.3.88.14570: . ack 66 win 14326 (ttl 64, id 186)
18:11:20.000000 kakofonix.posnet.com.telnet > 1.2.3.88.14570: P 40:89(49) ack 66 win 14335 (ttl 64, id 187)
18:11:20.000000 1.2.3.88.14570 > kakofonix.posnet.com.telnet: . ack 89 win 1024 (ttl 100, id 7)
18:11:20.000000 kakofonix.posnet.com.telnet > 1.2.3.88.14570: P 89:91(2) ack 66 win 14335 (ttl 64, id 188)
18:11:20.000000 1.2.3.88.14570 > kakofonix.posnet.com.telnet: . ack 91 win 1024 (ttl 100, id 8)
18:11:20.000000 kakofonix.posnet.com.telnet > 1.2.3.88.14570: P 91:108(17) ack 66 win 14335 (ttl 64, id 189)
18:11:20.000000 1.2.3.88.14570 > kakofonix.posnet.com.telnet: . ack 108 win 1024 (ttl 100, id 9)


I have tested this with 1.3.74 kernel with forwarding and masquerading
option enabled and disabled and on 1.3.77 with:

TCP/IP networking (CONFIG_INET) [Y/n/?]
IP: forwarding/gatewaying (CONFIG_IP_FORWARD) [Y/n/?]
IP: multicasting (CONFIG_IP_MULTICAST) [N/y/?]
IP: firewalling (CONFIG_IP_FIREWALL) [Y/n/?]
IP: accounting (CONFIG_IP_ACCT) [N/y/?]
IP: optimize as router not host (CONFIG_IP_ROUTER) [N/y/?]
IP: tunneling (CONFIG_NET_IPIP) [N/y/m/?]
IP: firewall packet logging (CONFIG_IP_FIREWALL_VERBOSE) [Y/n/?]
IP: masquerading (ALPHA) (CONFIG_IP_MASQUERADE) [Y/n/?]
*
* (it is safe to leave these untouched)
*
IP: PC/TCP compatibility mode (CONFIG_INET_PCTCP) [N/y/?]
IP: Reverse ARP (CONFIG_INET_RARP) [N/y/m/?]
IP: Disable Path MTU Discovery (normally enabled)
(CONFIG_NO_PATH_MTU_DISCOVERY) [N/y/?]
IP: Disable NAGLE algorithm (normally enabled) (CONFIG_TCP_NAGLE_OFF)
[N/y/?]
IP: Drop source routed frames (CONFIG_IP_NOSR) [Y/n/?]
IP: Allow large windows (not recommended if <16Mb of memory)
(CONFIG_SKB_LARGE) [N/y/?]

The same NCSA telnet configuration works with 1.2.13 kernel.

Do you have any ideas ?

I will try with 'Drop source routed frames' set to NO in a moment, but I'm
almost sure it won't change anything ........

[45 minutes later]

I was absolutely right. I don't try setting 'PC/TCP compatibility mode' to
YES, because I'm absolutely sure I have never set it in 1.2.13.


If you have any ideas or need additional information or testing, feel free
to write me even at 8 in the morning :-)


Jacek Zapala




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