Only the -ol options which act when a socket is bound (SO_REUSEADDR,
SO_REUSEPORT, SO_EXCLUSIVEADDRUSE, SO_PORT_SCALABILITY,
SO_REUSE_UNICASTPORT, IP_TRANSPARENT, TCP_FASTOPEN) must be the same
for a socket to be taken over. The others are set on the socket taken
over, those no longer given turned off; TCP_MAXSEG, whose default is
not 0, still needs a new socket when it is dropped.
Several services may still share an address, in one configuration or
across reloads: each new one takes over a listener of its own, one of
an old service of its type first, or opens another.
A service connecting back (-r) has no socket to share, but now a
listener without one for the place it connects to: on a reload the new
service connecting to the same place takes it over, and the old
service's clients are re-authenticated as its clients, as a listening
service's are.
Nothing moves from srvparam to the listener: its socket is what accept
and UDP sessions use, and the rest is the service's configuration,
which the listener only copies to compare.
Tests: a live option changed keeps the socket, a bind-time one makes
another, two services on one address are both taken over, and a
download through a connect-back service goes on or is cut as its user
is kept or removed. 3proxy(8) describes the takeover and
re-authentication.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
A service's TCP listening socket is kept as a listener: when a reload
commits, before the old services are told to stop, each new service
takes over the listener of an older configuration's service on the same
address, port, network namespace and device with the same -ol options.
It skips socket() and bind(), calling only listen() again for its own
backlog, and logs "Accepting connections, taken over". The old service
stops accepting at its next poll and lets go of the socket; whoever
lets go last closes it, unlinking a Unix socket's path.
So a service staying where it was no longer leaves a gap: before, the
old one closed its socket and the new one opened another, and a
connection queued on the old socket was reset. UDP services, whose
clients read from the service's socket, and two services of the same
configuration on one address keep their own sockets as before.
A test case makes requests nonstop through three reloads and wants none
refused or reset; against the build before this, connections were
reset. The reload case no longer waits out the switch. SIGUSR1 in
3proxy(8) describes how a reload behaves now.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
