Hello, Recently, we were trying to segment our account provisioning using HAProxy. We are having HAProxy to port NAT traffic to a backend, using the djb2 hash to select the backend based on the Host header. When attempting to predict the backend that HAProxy would select, we were unable to come to the same results as HAProxy did.
We dove into the code that HAProxy used to implement the djb2 hash, and discovered a bug in the map_get_server_hash function declaration. Where in the rest of the code, it uses an unsigned long for the hash value, the map_get_server_hash function uses an unsigned int. The end result is that we have a consistent value chosen for a backend by HAProxy, but one that is unpredictable by a standard implementation of djb2. Attached is the patch we used that resolved this issue. -- Dan.
haproxy_fix_map_hash.patch
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