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author | 2025-04-24 10:35:19 -0400 | |
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committer | 2025-04-29 16:22:25 +0200 | |
commit | 65e9024643c7512ade3aedbb341e11d77ed7abc2 (patch) | |
tree | 22d3bace43743c3c4038d61febfc68d6040b8025 /tools/perf/scripts/python/export-to-postgresql.py | |
parent | ipv4: prefer multipath nexthop that matches source address (diff) | |
download | wireguard-linux-65e9024643c7512ade3aedbb341e11d77ed7abc2.tar.xz wireguard-linux-65e9024643c7512ade3aedbb341e11d77ed7abc2.zip |
ip: load balance tcp connections to single dst addr and port
Load balance new TCP connections across nexthops also when they
connect to the same service at a single remote address and port.
This affects only port-based multipath hashing:
fib_multipath_hash_policy 1 or 3.
Local connections must choose both a source address and port when
connecting to a remote service, in ip_route_connect. This
"chicken-and-egg problem" (commit 2d7192d6cbab ("ipv4: Sanitize and
simplify ip_route_{connect,newports}()")) is resolved by first
selecting a source address, by looking up a route using the zero
wildcard source port and address.
As a result multiple connections to the same destination address and
port have no entropy in fib_multipath_hash.
This is not a problem when forwarding, as skb-based hashing has a
4-tuple. Nor when establishing UDP connections, as autobind there
selects a port before reaching ip_route_connect.
Load balance also TCP, by using a random port in fib_multipath_hash.
Port assignment in inet_hash_connect is not atomic with
ip_route_connect. Thus ports are unpredictable, effectively random.
Implementation details:
Do not actually pass a random fl4_sport, as that affects not only
hashing, but routing more broadly, and can match a source port based
policy route, which existing wildcard port 0 will not. Instead,
define a new wildcard flowi flag that is used only for hashing.
Selecting a random source is equivalent to just selecting a random
hash entirely. But for code clarity, follow the normal 4-tuple hash
process and only update this field.
fib_multipath_hash can be reached with zero sport from other code
paths, so explicitly pass this flowi flag, rather than trying to infer
this case in the function itself.
Signed-off-by: Willem de Bruijn <willemb@google.com>
Reviewed-by: David Ahern <dsahern@kernel.org>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Ido Schimmel <idosch@nvidia.com>
Link: https://patch.msgid.link/20250424143549.669426-3-willemdebruijn.kernel@gmail.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Diffstat (limited to 'tools/perf/scripts/python/export-to-postgresql.py')
0 files changed, 0 insertions, 0 deletions