The tap+relay intern-ping test and the DNS hostname-ping test both
flaked intermittently (roughly 1 in 13-20 runs), always in a "found_success
== false" shape with no assertion-level clue as to why.
Root cause, confirmed via a temporary production-code diagnostic (since
reverted) and cross-referenced against network_join.cpp's own code: the
readiness poll only waited for eth0 to *exist* (`ip link show eth0`), but
an interface can become visible before join_one_network()'s own later
`ip addr add`/`ip link set ... up` steps for it have actually run. A
script that used the interface as soon as it merely existed could ping,
get "Network unreachable" (no address yet), and exit almost immediately
-- and since a session's own sandboxed process is the sole occupant of
its pid/net namespace (--unshare-pid/--unshare-net), its exit destroys
that namespace outright. That, in turn, made whichever other nsenter
call was still in flight against the same namespace -- join_one_network()'s
own remaining steps, or the entirely separate per-session DNS resolver
(network_dns.cpp's start_dns_resolver(), which enters every networked
session's namespace regardless of whether --hostname was given) -- fail
with "No such file or directory" against a namespace that had already
collapsed underneath it.
This is the same general class of race network_join.{h,cpp}'s own
CLAUDE.md entry already documents (a very-short-lived sandboxed command
can outrun its own concurrent network setup), just one step further than
the eth0-existence race already fixed earlier in this file -- a test-code
issue, not a production bug. Fixed by polling for an actually assigned
address on eth0 instead of mere existence, in both wait_for_eth0_then()
and BackgroundPeer's own inline readiness script.
Verified with the diagnostic in place that the DNS resolver's own
namespace lookup was never itself stale, isolating the cause to the
script's own premature exit. Re-verified extensively after the fix:
8/8 isolated repeats of the previously-flaky tap+relay test, and 6
consecutive full [integration][root][net] suite runs (78 test-case
executions total) with no failures.
ceamac
7c33375d4d