[rootusrootus]

Unless you tell it not to, ping will try a reverse lookup on the IP you are pinging in order to display that to you in the output. It's a good idea to keep that in mind when you ping something, especially if you notice the first ping is abnormally slow.

[dingo_bat]

That reverse lookup time is not counted in the first ping.

[rootusrootus]

Perhaps that depends on operating system. In the 30 years I have been using ping on Linux, the reverse lookup time is absolutely included in the first ping time.

[dingo_bat]

If true, that's a bug.

Edit: Assuming this is the right file: https://github.com/iputils/iputils/blob/master/ping.c, I don't see the reverse lookup code anywhere. But then I'm not the most proficient in reading linux code.