listener: emit warnings on EPERM

In retrospect, warnings for EPERM on accept4(2) failure may
help detect misconfigured firewalls, so start emitting warnings
for EPERM.  Fwiw, I've never known excessive EPERM warnings
to be excessively noisy in other TCP services I've run over
the years.

1 files changed, 2 insertions, 6 deletions

diff --git a/lib/PublicInbox/Listener.pm b/lib/PublicInbox/Listener.pm
index 09f1f2e5..7cedc349 100644
--- a/lib/PublicInbox/Listener.pm
+++ b/lib/PublicInbox/Listener.pm
@@ -8,7 +8,7 @@ use parent 'PublicInbox::DS';
 use Socket qw(SOL_SOCKET SO_KEEPALIVE IPPROTO_TCP TCP_NODELAY);
 use IO::Handle;
 use PublicInbox::Syscall qw(EPOLLIN EPOLLEXCLUSIVE);
-use Errno qw(EAGAIN ECONNABORTED EPERM);
+use Errno qw(EAGAIN ECONNABORTED);
 
 # Warn on transient errors, mostly resource limitations.
 # EINTR would indicate the failure to set NonBlocking in systemd or similar
@@ -38,13 +38,9 @@ sub event_step {
                 IO::Handle::blocking($c, 0); # no accept4 :<
                 eval { $self->{post_accept}->($c, $addr, $sock) };
                 warn "E: $@\n" if $@;
-        } elsif ($! == EAGAIN || $! == ECONNABORTED || $! == EPERM) {
+        } elsif ($! == EAGAIN || $! == ECONNABORTED) {
                 # EAGAIN is common and likely
                 # ECONNABORTED is common with bad connections
-                # EPERM happens if firewall rules prevent a connection
-                # on Linux (and everything that emulates Linux).
-                # Firewall rules are sometimes intentional, so we don't
-                # warn on EPERM to avoid being too noisy...
                 return;
         } elsif (my $sym = $ERR_WARN{int($!)}) {
                 warn "W: accept(): $! ($sym)\n";