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2623e0a0b7
CIDs are provided by haproxy so that the peer can use them as DCID of its packets. Their value is set via a random generator. It happens on several occasions during connection lifetime: * via ODCID derivation if haproxy is the server * on quic_conn init if haproxy is the client * during post-handshake if haproxy is the server * on RETIRE_CONNECTION_ID frame parsing CIDs are stored in a global tree. On ODCID derivation, a check is performed to ensure the CID is not a duplicate value. This is mandatory to properly handle multiple INITIAL packets from the same client on different thread. However, for the other cases, no check is performed for CID collision. As _quic_cid_insert() is silent, the issue is not detected at all. This results in a CID advertized to the peer but not stored in the global one. In the end, this may cause two issues. The first one is that packets from the client which use the new CID will be rejected by haproxy, most probably with a STATELESS_RESET. The second issue is that it can cause a crash during quic_conn release. Indeed, the CID is stored in the quic_conn local tree and thus eb_delete() for the global tree will be performed. As <leaf_p> member is uninit, this results in a segfault. Note that this issue is pretty rare. It can only be observed if running with a high number of concurrent connections in parallel, so that the random generator will provide duplicate values. Patch is still labelled as MEDIUM as this modifies code paths used frequently. To fix this, _quic_cid_insert() unsafe function is completely removed. Instead, quic_cid_insert() can be used, which reports an error code if a collision happens. CID are then stored in the quic_conn tree only after global tree insert success. Here is the solution for each steps if a collision occurs : * on init as client: the connection is completely released * post-handshake: the CID is immediately released. The connection is kept, but it will miss an extra CID. * on RETIRE_CONNECTION_ID parsing: a loop is implemented to retry random generation. It it fails several times, the connection is closed in error. A small convenience change is made to quic_cid_insert(). Output parameter <new_tid> can now be NULL, which is useful as most of the times caller do not care about it. This must be backported up to 2.6.