[Dnsmasq-discuss] Issues with DNSMASQ Retries using same port

[Singh, Prashant]

Hi Simon,

Thanks for the reply. I am curious about what could be the potential consequences of this change in behavior. Would you please help me understand, wondering if that would put us in different problem?

Also would introducing  a new flag just for this feature be helpful in this case ?

Thanks,
Prashant 

On 2/25/22, 3:21 PM, "Dnsmasq-discuss on behalf of Simon Kelley" <dnsmasq-discuss-bounces at lists.thekelleys.org.uk on behalf of simon at thekelleys.org.uk> wrote:

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    On 25/02/2022 21:25, Singh, Prashant via Dnsmasq-discuss wrote:
    > Hi Simon,
    >
    > We use DNSMASQ for resolving/forwarding the dns queries of the
    > applications hosted. We started seeing a few errors in dns resolutions.
    > We investigated and found that the issue was due to the corrupted
    > network path the request took. And it takes around 7 to 8 secs for
    > network path taken to heal, hence all the retries were also failing as
    > they took same network path.
    >
    > We were exploring ways if we can force the dnsmasq to use different
    > source port for retries so that retried requests can take random network
    > path rather than bad network path.
    >
    > I wanted to know the reasoning behind (if there is) the choice of using
    > the same source port for retries. And is it possible to have a
    > patch/flag in dnsmasq to update this logic?

    Dnsmasq treats file descriptors and source ports as a scarce resource
    and re-uses when it can, without affecting security.

    The logic is in the function allocate_rfd(), and it would be fairly
    trivial to change the behavior, but there might be unexpected
    consequences under load.


    Cheers,

    Simon.





    >
    > Thanks,
    >
    > Prashant
    >
    >
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