bug#47431: Process Whois connection broken by remote peer.

[Hongyi Zhao]

On Sun, Mar 28, 2021 at 2:38 PM Eli Zaretskii <eliz@gnu.org> wrote:
>
> > From: Hongyi Zhao <hongyi.zhao@gmail.com>
> > Date: Sun, 28 Mar 2021 09:41:20 +0800
> > Cc: 47431@debbugs.gnu.org
> >
> > > I think that's unrelated, so I don't understand why it hangs
> > > indefinitely for you.  Are you sure you waited enough time before
> > > giving up?
> >
> > It will hang up there forever.
>
> Maybe your network connection blocks some addresses or something?
> Otherwise, how to explain that it doesn't block for me?

I further debug this problem with tcpdump for a runing `emcas -Q`
process, as described below.

For `M-x whois RET gnu.org RET`, when the query succeeds, the
following info will be captured:

$ sudo tcpdump -i any port 43
tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on any, link-type LINUX_SLL (Linux cooked v1), capture size
262144 bytes
15:00:29.061914 IP6 X10DAi.56918 >
whois.publicinterestregistry.net.whois: Flags [S], seq 1929893031, win
64440, options [mss 1432,sackOK,TS val 417951633 ecr 0,nop,wscale 7],
length 0
15:00:29.398867 IP6 whois.publicinterestregistry.net.whois >
X10DAi.56918: Flags [S.], seq 1816069595, ack 1929893032, win 1440,
options [mss 1379,nop,nop,TS val 2007125977 ecr 417951633,sackOK,eol],
length 0
15:00:29.398923 IP6 X10DAi.56918 >
whois.publicinterestregistry.net.whois: Flags [.], ack 1, win 64440,
options [nop,nop,TS val 417951970 ecr 2007125977], length 0
15:00:29.399038 IP6 X10DAi.56918 >
whois.publicinterestregistry.net.whois: Flags [P.], seq 1:10, ack 1,
win 64440, options [nop,nop,TS val 417951970 ecr 2007125977], length 9
15:00:30.297592 IP6 X10DAi.56918 >
whois.publicinterestregistry.net.whois: Flags [P.], seq 1:10, ack 1,
win 64440, options [nop,nop,TS val 417952869 ecr 2007125977], length 9
15:00:31.321603 IP6 X10DAi.56918 >
whois.publicinterestregistry.net.whois: Flags [P.], seq 1:10, ack 1,
win 64440, options [nop,nop,TS val 417953893 ecr 2007125977], length 9
15:00:31.339068 IP6 whois.publicinterestregistry.net.whois >
X10DAi.56918: Flags [P.], seq 1:1368, ack 10, win 2880, options
[nop,nop,TS val 2007127334 ecr 417952869], length 1367
15:00:31.339120 IP6 X10DAi.56918 >
whois.publicinterestregistry.net.whois: Flags [.], ack 1368, win
63073, options [nop,nop,TS val 417953910 ecr 2007127334], length 0

For `M-x whois RET baidu.com RET`, when the query fails, the following
info will be captured:

$ sudo tcpdump -i any port 43
tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on any, link-type LINUX_SLL (Linux cooked v1), capture size
262144 bytes
15:05:24.433913 IP X10DAi.47186 > 198.41.3.79.whois: Flags [S], seq
1963456950, win 64240, options [mss 1460,sackOK,TS val 2174254150 ecr
0,nop,wscale 7], length 0
15:05:25.465604 IP X10DAi.47186 > 198.41.3.79.whois: Flags [S], seq
1963456950, win 64240, options [mss 1460,sackOK,TS val 2174255182 ecr
0,nop,wscale 7], length 0
15:05:27.481605 IP X10DAi.47186 > 198.41.3.79.whois: Flags [S], seq
1963456950, win 64240, options [mss 1460,sackOK,TS val 2174257198 ecr
0,nop,wscale 7], length 0

I also will see the following in *Messages* buffer:

For information about GNU Emacs and the GNU system, type C-h C-a.
open-network-stream: Failed connect: No route to host

Regards
-- 
Assoc. Prof. Hongyi Zhao <hongyi.zhao@gmail.com>
Theory and Simulation of Materials
Hebei Polytechnic University of Science and Technology engineering
NO. 552 North Gangtie Road, Xingtai, China