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Posted to commits@nuttx.apache.org by "zhhyu7 (via GitHub)" <gi...@apache.org> on 2026/04/22 09:04:20 UTC
[PR] netlib: support checkipconnectivity when use reslov.conf [nuttx-apps]
zhhyu7 opened a new pull request, #3460:
URL: https://github.com/apache/nuttx-apps/pull/3460
## Summary
Improve netlib_check_ipconnectivity() to support DNS nameservers from resolv.conf via dns_foreach_nameserver(), instead of relying on the compile-time CONFIG_NETDB_DNSSERVER_IPv4ADDR macro.
## Impact
- Add dns_ping_callback() to iterate over all configured DNS nameservers and ping each one until a reply is received.
- When ip is NULL, use dns_foreach_nameserver() to dynamically resolve and ping DNS servers at runtime, replacing the previous #ifdef CONFIG_NETDB_DNSSERVER_IPv4ADDR compile-time approach.
- When ip is provided, ping the specified address directly (behavior unchanged).
- Fix missing newline at end of file.
## Testing
Verify netlib_check_ipconnectivity(NULL, ...) pings DNS servers from resolv.conf and ram.
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Re: [PR] netlib: support checkipconnectivity when use reslov.conf [nuttx-apps]
Posted by "zhhyu7 (via GitHub)" <gi...@apache.org>.
zhhyu7 closed pull request #3460: netlib: support checkipconnectivity when use reslov.conf
URL: https://github.com/apache/nuttx-apps/pull/3460
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Re: [PR] netlib: support checkipconnectivity when use reslov.conf [nuttx-apps]
Posted by "zhhyu7 (via GitHub)" <gi...@apache.org>.
zhhyu7 commented on PR #3460:
URL: https://github.com/apache/nuttx-apps/pull/3460#issuecomment-4296675420
> @zhhyu7 it's not a good method to use ping to check if DNS server is reachable. Here is the reason: A DNS server is only required to answer DNS queries on port 53 over UDP/TCP. Replying to ping means replying to ICMP Echo, which is separate and optional.
>
> So a DNS server may:
>
> * answer DNS normally
> * ignore or block ping
> * be behind a firewall that drops ICMP
>
> If you want to test DNS reachability, use a DNS query like nslookup, dig, or host, not ping.
>
> And we need move further: It's not good practice to just check network connectivity via ping ipv4 address, the device may just have an IPv6 address only.
@masc2008, You're right. Regarding NTP, I think we should directly remove the netlib_check_ipconnectivity check from the ntpclient file, because we already have backoff behavior to avoid screen flooding. Meanwhile, I will add a new patch later to select a more appropriate IP address for the check, such as DRaddr, and also add support for IPv6 addresses.
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Re: [PR] netlib: support checkipconnectivity when use reslov.conf [nuttx-apps]
Posted by "masc2008 (via GitHub)" <gi...@apache.org>.
masc2008 commented on PR #3460:
URL: https://github.com/apache/nuttx-apps/pull/3460#issuecomment-4296440895
@zhhyu7 it's not a good method to use ping to check if DNS server is reachable. Here is the reason:
A DNS server is only required to answer DNS queries on port 53 over UDP/TCP. Replying to ping means replying to ICMP Echo, which is separate and optional.
So a DNS server may:
- answer DNS normally
- ignore or block ping
- be behind a firewall that drops ICMP
If you want to test DNS reachability, use a DNS query like nslookup, dig, or host, not ping.
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Re: [PR] netlib: support checkipconnectivity when use reslov.conf [nuttx-apps]
Posted by "masc2008 (via GitHub)" <gi...@apache.org>.
masc2008 commented on PR #3460:
URL: https://github.com/apache/nuttx-apps/pull/3460#issuecomment-4296756470
thanks! Good job HongYu!👍
On Wed, 22 Apr 2026 at 21:39, zhhyu7 ***@***.***> wrote:
> *zhhyu7* left a comment (apache/nuttx-apps#3460)
> <https://github.com/apache/nuttx-apps/pull/3460?email_source=notifications&email_token=AEIQS6OZIYF2Y6WWNXTS7F34XDDRLA5CNFSNUABFM5UWIORPF5TWS5BNNB2WEL2JONZXKZKDN5WW2ZLOOQXTIMRZGY3DONJUGIYKM4TFMFZW63VHNVSW45DJN5XKKZLWMVXHJNLQOJPWG33NNVSW45C7N5YGK3S7MNWGSY3L#issuecomment-4296675420>
>
> @zhhyu7 <https://github.com/zhhyu7> it's not a good method to use ping to
> check if DNS server is reachable. Here is the reason: A DNS server is only
> required to answer DNS queries on port 53 over UDP/TCP. Replying to ping
> means replying to ICMP Echo, which is separate and optional.
>
> So a DNS server may:
>
> - answer DNS normally
> - ignore or block ping
> - be behind a firewall that drops ICMP
>
> If you want to test DNS reachability, use a DNS query like nslookup, dig,
> or host, not ping.
>
> And we need move further: It's not good practice to just check network
> connectivity via ping ipv4 address, the device may just have an IPv6
> address only.
>
> @masc2008 <https://github.com/masc2008>, You're right. Regarding NTP, I
> think we should directly remove the netlib_check_ipconnectivity check from
> the ntpclient file, because we already have backoff behavior to avoid
> screen flooding. Meanwhile, I will add a new patch later to select a more
> appropriate IP address for the check, such as DRaddr, and also add support
> for IPv6 addresses.
>
> —
> Reply to this email directly, view it on GitHub
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