bug#40665: 28.0.50; tls hang on local ssl

[Derek Zhou <derek@3qin.us>]

Robert Pluim writes:

>>>>>> On Thu, 16 Apr 2020 14:06:30 +0000 (UTC), Derek Zhou <derek@3qin.us> said:
>
>     Derek> I have a vps that have ssl cert from let's encrypt. If I run emacs on
>     Derek> that machine and use eww to open the local url through proper DNS name,
>     Derek> it hangs. This only happen with gnutls 3.6+ I believe. w3m works.
>
> w3m uses OpenSSL rather than GnuTLS, I think.
True, however, wget works, which use gnutls.
>
>     Derek> recipe:
>     Derek> emacs -q
>     Derek> M-x eww
>     Derek> https://u15789687.ct.sendgrid.net/ls/click?upn=5u6PACFCQRlPqbnHSU4z2Xlc-2BdngjKawFESXJ7OrOF8M0VhErToh587OqGs4rdXCYpHS-2BTJCwQlyeoYpCGakF7HeU0y-2ByPTUfBl7m1gchyt8f9DppJ79-2BiI84YXNxbHvWRJyYFbi8O0HbKvvdS1ddux3ZjncA02WH4UyER8c34I-2BD7sN4tF1vdNkjAh9119T1Vnevpw0iFcIaCldIwi3pFMJra8DmFvLPm-2FF8zihX-2Bst0h8NJYZr3qoni6nP4cpeyRUK7caO86OxFnwGl-2FDd-2BC2aJe2MQ3-2BUedR5rO98PGM2qC9CmZpHC6LeditpbEMg30SLXsj-2B-2F7LCBhBfjmHD0OLTr-2BHtEiIkdcnftf1TZuxGU-2FLZzlzKMdeUjJElVAwbHa6NnmjFvW6U1NyGilkkC-2FutAlHDaF8hwDB5aRdmIV7VO9hYnp0sJL2jW76MLyjoD3UMd0cndm-2FfRdMPrnhiDAQlj-2F2atQr-2F0YiEMsOTdF034xF-2BsahDF55iuCkyKFQEQPKTIBSn6j76ME2zRj4-2BVw-3D-3D_U2j_S71vn-2BdJ969jmJsMZjcAVQ4Mbh84GRhJ0erfBn5ySXu1Uwk8oEkEaLtN1f5KRaKw1GkGOL1TU5kIB15t6oXeTDhu8J6Q7nTz-2FKhR7YJaupyvWQhgCTiCw1iDgSo5HtcOHBVcSQpRwOWOSozqTdtwd1p
 CWcPFeLcdQ1RBNsisdkYedrggCQGsUES4VBHJOYw-2FYGjkvEi2iyte2vifaqFXX2XlbbjnToTO6WQMa2ynzhPCWiWpfoD2XIbEMU3FUeNA
Sorry, the crazy sendgrid munge links. it was mail.3qin.us
>
>     Derek> This only happens when running on mail.3qin.us itself; from across the
>     Derek> network it is ok. I believe it is timing related and worsen by very
>     Derek> short network latency and small files.
>
> Which version exactly of GnuTLS are you running? Is it possible for
> you to do a local install of a newer version and try that with emacs?
I am using Debian 10, standard gnutls version
ii  libgnutls-openssl27:amd64          3.6.7-4+deb10u2                amd64        GNU TLS library - OpenSSL wrapper
ii  libgnutls28-dev:amd64              3.6.7-4+deb10u2                amd64        GNU TLS library - development files
I don't want to mess up system libraries; if there is a way to compile a
gnutls locally and link emacs with it statically, I can try.
>
> Otherwise, maybe turning off TLS1.3 will help:
>
>     (setq gnutls-algorithm-priority "NORMAL:-VERS-TLS1.3")
>
Does not help.

> Another thing to try is setting 'gnutls-log-level' to progressively
> higher values, to see if it resolves the timing issues.
1 or 2 will give me more informational prints; with or without the
following; but always hang. 3 does not seem to have any effect.

gnutls.c: [1] (Emacs) non-fatal error: Resource temporarily unavailable,
try again.

I've tried 26.3, latest git (28.0.??) latest emacs-27 (27.0.9?) and they
all behave the same.

Derek