getsockopt(fd, SOL_IP, SO_ORIGINAL_DST, sa, &salen) is in fact sometimes returning the source IP instead the destination IP.

[roobesh ganapathy mohandass]

We are using below version of Ubuntu/kernel,

~# lsb_release -rd
Description: Ubuntu 18.04.1 LTS
Release: 18.04

What you expected to happen:
getsockopt(fd, SOL_IP, SO_ORIGINAL_DST, sa, &salen) - should return always destination IP(connected IP).

What happened instead:
getsockopt(fd, SOL_IP, SO_ORIGINAL_DST, sa, &salen) is in fact sometimes returning the source IP instead the destination IP. Using getsockname() instead looks like solving the issue.

For just an example: Out of 6569124 requests , 4 requests were wrong 0.000060891 % (this is just an rough estimate to give you idea on frequency)

Some old reference:
https://stackoverflow.com/questions/11417187/getsockopt-so-original-dst-occasionally-returns-client-address

We searched in launchpad for any bug filed for this but couldn't see any. Hence filing this behavior here.

Side Note: (about how we identified this behavior)
We were using haproxy-version 1.8.14-1 which is using this kernel function getsockopt(fd, SOL_IP, SO_ORIGINAL_DST, sa, &salen) to get the destination IP details/connected address details. But instead we are getting very occasional source IP address instead of destination(Connected IP).