c-ares / c-ares / 28687671653

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push

github

Committed by web-flow

Commit Message

ares_dns_parse: reject responses with more than one OPT record (RFC 6891) (#1189)

RFC 6891 §6.1.1 states a message MUST NOT contain more than one OPT
resource record. The parser accepted any number of OPT RRs in the
additional section without complaint.

### Change
After parsing the additional section in `ares_dns_parse_buf`, count the
OPT records and return `ARES_EBADRESP` (format error) if more than one
is present.

### Tests
- `ParseSingleOpt` — a single OPT still parses successfully (regression
guard).
- `ParseMultipleOptRejected` — a response carrying two OPT records is
rejected with `ARES_EBADRESP`. (Verified the test fails without the
fix.)

Fixes #1137

Signed-off-by: Brad House <brad@brad-house.com>

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