ok.. so here is my best guess as to whats going on with regards to this error with the 'empty' protocol list...
it looks like the 'rogue' client is possibly sending a \0 or some other 'garbage' non-printable character(s) as 
a protocol.  this is the reason why len > 0, but the requested protocol appears to be 'empty'

On Wed, May 3, 2017 at 3:08 PM, Bryan Call <bcall@apache.org> wrote:
I looked through our produciton logs on all our servers (a lot of servers) and I am seeing this too once in awhile.  It shouldn’t print the log unless len > 0, but from the logs it looks like the length is 0.

It might be helpful to also print len to see what the value is.  Can you please file an issue on this?

Link to issues:

Thank you,


On May 3, 2017, at 12:23 PM, Jeremy Payne <jp557198@gmail.com> wrote:

ERROR: failed to find registered SSL endpoint for ''

ATS 6.1.1
Built against RHEL-openssl 1.0.1e-fips

Has anyone identified any legacy/broken clients out in the wild that may be responsible for causing these errors ?
I cant seem to generate the same error using openssl:

openssl s_client  -connect ip:port  -nextprotoneg ''

If I pass an empty list, ATS just returns a list of supported protocols and closes the TLS connection. Which is per spec(if i read correctly). 

The request must be flawed some other way for ATS to generate this error. 
I can't run debug or packet capture on these machines since they are in production
The error seems somewhat innocent.. I am guessing what I may find is that these
errors are caused by some broken/incomplete client/TLS implementation.  I am leaning towards
this being something amiss with early implementations of boringssl. 

However, while I am testing some older clients I am putting this out to the community.
Maybe someone here has already identified some broken clients or identified a general area
causing these errors to generate.