** Description changed: + [Impact] + + TCP stub is cutting down the payload to 512 bytes when EDNS is disabled. + This makes non-EDNS clients (nslookup) receive a "shortened" answer even + when UDP returns a truncated reply for a new TCP query. For instance, + + - If the client supports EDNS: + + $ dig +noall +answer testing.irongiantdesign.com @127.0.0.53 | wc -l + 30 + + - If the client does not support EDNS: + + $ dig +noedns +noall +answer testing.irongiantdesign.com @127.0.0.53 | wc -l + 29 + + In the second case, no-EDNS, TCP should provide the complete answer, but + it's capped at UDP's size. + + [Test Case] + + Query systemd-resolved with a domain name that resolves to multiple + (lots.. 30+) A records. A client with EDNS support (dig) will receive + all of them, a client without support (nslookup or dig +noedns) will + have a truncated list. + + [Regression potential] + + Minimal. This change only affects TCP requests, and the new size is + already used in the code for other requests. + + [Other Info] + + Upstream bug: https://github.com/systemd/systemd/issues/10816 + Fixed upstream with commit: https://github.com/systemd/systemd/commit/e6eed9445956cfa496e1db933bfd3530db23bfce + + [Original Description] + Querying a domain name that has >512 bytes in records (e.g. 30+ A records), the number of results depends on the DNS client used: - If the client supports EDNS: $ dig +noall +answer testing.irongiantdesign.com @127.0.0.53 | wc -l - 30 + 30 - If the client does not support EDNS: $ dig +noedns +noall +answer testing.irongiantdesign.com @127.0.0.53 | wc -l 29 Normally a client that doesn't support EDNS would receive a truncated reply from the initial UDP connection (limited by the spec to 512 bytes) and a second query would be established via TCP to receive the complete results. In this case, the number of results is the same regardless of the protocol used (29). Upstream bug: https://github.com/systemd/systemd/issues/10816
** Description changed: [Impact] TCP stub is cutting down the payload to 512 bytes when EDNS is disabled. This makes non-EDNS clients (nslookup) receive a "shortened" answer even when UDP returns a truncated reply for a new TCP query. For instance, - If the client supports EDNS: $ dig +noall +answer testing.irongiantdesign.com @127.0.0.53 | wc -l 30 - If the client does not support EDNS: $ dig +noedns +noall +answer testing.irongiantdesign.com @127.0.0.53 | wc -l 29 In the second case, no-EDNS, TCP should provide the complete answer, but it's capped at UDP's size. [Test Case] Query systemd-resolved with a domain name that resolves to multiple (lots.. 30+) A records. A client with EDNS support (dig) will receive all of them, a client without support (nslookup or dig +noedns) will - have a truncated list. + have a truncated list. Using the example above: + + EDNS: dig +noall +answer testing.irongiantdesign.com @127.0.0.53 | wc -l + non-EDNS: dig +noedns +noall +answer testing.irongiantdesign.com @127.0.0.53 | wc -l [Regression potential] Minimal. This change only affects TCP requests, and the new size is already used in the code for other requests. [Other Info] Upstream bug: https://github.com/systemd/systemd/issues/10816 Fixed upstream with commit: https://github.com/systemd/systemd/commit/e6eed9445956cfa496e1db933bfd3530db23bfce [Original Description] Querying a domain name that has >512 bytes in records (e.g. 30+ A records), the number of results depends on the DNS client used: - If the client supports EDNS: $ dig +noall +answer testing.irongiantdesign.com @127.0.0.53 | wc -l 30 - If the client does not support EDNS: $ dig +noedns +noall +answer testing.irongiantdesign.com @127.0.0.53 | wc -l 29 Normally a client that doesn't support EDNS would receive a truncated reply from the initial UDP connection (limited by the spec to 512 bytes) and a second query would be established via TCP to receive the complete results. In this case, the number of results is the same regardless of the protocol used (29). Upstream bug: https://github.com/systemd/systemd/issues/10816 -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1804487 Title: systemd-resolved has issues when the answer is over 512 bytes with EDNS disabled To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/systemd/+bug/1804487/+subscriptions -- ubuntu-bugs mailing list [email protected] https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
