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Differential D21351

ping: do reverse DNS lookup for a reply by default
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Authored by jansucan on Aug 21 2019, 1:57 PM.
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rS351330: ping: do reverse DNS lookup of the target address
Summary

Do reverse DNS lookup for a reply by default

Submitted by: Ján Sučan <sucanjan@gmail.com>
Sponsored by: Google LLC (Google Summer of Code 2019)

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rS FreeBSD src repository - subversion
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jansucan created this revision.Aug 21 2019, 1:57 PM
Harbormaster completed remote builds in B25992: Diff 61076.Aug 21 2019, 1:57 PM
jansucan mentioned this in D21338: ping6: make lookup of symbolic names in the reply default.Aug 21 2019, 2:03 PM
asomers accepted this revision.Aug 21 2019, 2:51 PM
This revision is now accepted and ready to land.Aug 21 2019, 2:51 PM
Closed by commit rS351330: ping: do reverse DNS lookup of the target address (authored by asomers). · Explain WhyAug 21 2019, 2:52 PM
This revision was automatically updated to reflect the committed changes.
asomers added a commit: rS351330: ping: do reverse DNS lookup of the target address.
Herald added a subscriber: imp. · View Herald TranscriptAug 21 2019, 2:52 PM
cem added a subscriber: cem.Aug 22 2019, 12:17 AM

Hm, I'm not sure I like this being the new default. I guess Linux does it, but there are or used to be many networks where reverse DNS was totally broken (as in, silently dropped). It is nice that ping is mostly a test of IP (ICMP) and not the higher level UDP/TCP protocols DNS uses.

Is there a very short timeout on rDNS lookup failure or on broken networks will ping just hang for 30 seconds at a time?

asomers added a comment.Aug 22 2019, 12:21 AM
In D21351#464706, @cem wrote:

Hm, I'm not sure I like this being the new default. I guess Linux does it, but there are or used to be many networks where reverse DNS was totally broken (as in, silently dropped). It is nice that ping is mostly a test of IP (ICMP) and not the higher level UDP/TCP protocols DNS uses.

Is there a very short timeout on rDNS lookup failure or on broken networks will ping just hang for 30 seconds at a time?

Personally, I could go either way for the default. What's most important IMHO is that ping and ping6 have the same default. Until now, they didn't.

cem added a comment.Aug 22 2019, 12:29 AM
In D21351#464707, @asomers wrote:

Personally, I could go either way for the default. What's most important IMHO is that ping and ping6 have the same default. Until now, they didn't.

I agree they should have the same default. But I think generally, where such defaults might conflict, the IPv4 version of the tool's default takes precedence. IPv4 is still the dominant protocol, as much as we'd all like that to change. The foo6 utilities are all secondary.

jansucan added a comment.Aug 22 2019, 8:13 AM

Maybe the title of this revision is not completely exact. The F_NUMERIC option flag has been cleared by default so it's more like ping was intended to do reverse lookups by default.

After reading opinions of both of you, I lean a bit more towards numeric only output being default. It will be done in the next diff.

asomers mentioned this in rS352371: MFC r351318, r351330, r351393, r351398, r351440, r351461, r351548, r352226….Sep 16 2019, 12:57 AM

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head/
sbin/
ping/
3 lines

Diff 61077

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head/sbin/ping/ping.c

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