dnsdist: Fix invalid proxy protocol payload on a DoH TC to TCP retry #11604
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dnsdist forwards incoming DoH queries to its backend over UDP, and retry over TCP if the response is truncated (TC=1). When the proxy protocol is used between dnsdist and its backend, the second query, over TCP, needs to take into account that the proxy protocol payload has already been handled. This was not properly done in that exact case because the proxy protocol payload length was not propagated to the code handling the TCP communication, leading to the query ID being edited at the wrong offset in the packet and thus to an invalid proxy protocol payload.
7 tasks
omoerbeek
reviewed
May 16, 2022
omoerbeek
approved these changes
May 16, 2022
8 tasks
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Short description
dnsdist forwards incoming DoH queries to its backend over UDP, and retry over TCP if the response is truncated (TC=1).
When the proxy protocol is used between dnsdist and its backend, the second query, over TCP, needs to take into account that the proxy protocol payload has already been handled. This was not properly done in that exact case because the proxy protocol payload length was not propagated to the code handling the TCP communication, leading to the query ID being edited at the wrong offset in the packet and thus to an invalid proxy protocol payload.
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