Re: [v3] net/ceph/messenger: support IPv6 Link-Local with scope identifier

Hi Max,

NACK for now. Thanks for the patch, but I have some concerns
that need a v2:

  1. [critical] messenger.c:1259: scope_id leaks into wire identity, breaking handshake
     `inet_pton_with_scope()` stores the local interface index in
     `sin6_scope_id`. The full `sockaddr_storage` — including
     `sin6_scope_id` — is copied into `ceph_entity_addr.in_addr`, which
     is then wire-encoded and `memcmp`'d during both v1 and v2
     handshakes. The server will have `scope_id=0` in its advertised
     address, so the comparison will always fail for link-local
     addresses with a scope. The interface index is also
     namespace-local, so it won't match across hosts even if both sides
     set one.
     Suggested fix: Zero out `sin6_scope_id` in the canonical
     `ceph_entity_addr` after the `memcpy`. Keep the scope only in the
     `sockaddr` passed to `kernel_connect()`, or store it in a side
     field.
  2. [minor] messenger.c:1334: Allocation failure masked by DNS fallback
     `ceph_pton()` can return `-ENOMEM` from `kstrndup()`, but
     `ceph_parse_server_name()` treats any non-zero return as "not an IP
     literal" and falls through to `ceph_dns_resolve_name()`. This
     silently turns OOM into a spurious DNS lookup.
     Suggested fix: Fall back to DNS only on `-EINVAL`; propagate
     `-ENOMEM` directly.
  3. [nit] messenger.c:1247: GFP_NOFS in non-filesystem context
     `kstrndup(str, len, GFP_NOFS)` is used during mount option parsing
     — process context, no filesystem locks held. `GFP_KERNEL` would be
     more appropriate.

scope_id from inet_pton_with_scope() is copied into the canonical ceph_entity_addr, breaking v1 and v2 handshake identity comparisons for link-local addresses


-- 
Alex Markuze