Bug 41291

$ cat ~/.distcc/hosts
--randomize
[fe80::216:3eff:feXX:YYZZ%enp1s0]/20
[fe80::216:3eff:feXX:YYZZ%enp1s0]/20
[fe80::216:3eff:feXX:YYZZ%enp1s0]/20
--localslots_cpp=60

$ cat > hello.c <<-EOF
#include <stdio.h>
int main(int argc, char **argv) {
  printf("Hello, world!\n");
  return 0;
}
EOF

$ distcc gcc -c hello.c
distcc[90392] (dcc_connect_by_name) ERROR: failed to look up host "fe80::216:3eff:fe66:f878%enp1s0": Unknown host
distcc[90392] (dcc_connect_by_name) ERROR: failed to look up host "fe80::216:3eff:fe9b:ed4a%enp1s0": Unknown host
distcc[90392] (dcc_connect_by_name) ERROR: failed to look up host "fe80::216:3eff:fea6:5c5d%enp1s0": Unknown host
distcc[90392] Warning: failed to distribute hello.c to [fe80::216:3eff:fea6:5c5d%enp1s0]/20, running locally instead

$ rm -f ~/.distcc/lock/backoff_tcp_*

$ env DISTCC_VERBOSE=1 distcc gcc -c hello.c

distcc[90365] (dcc_trace_version) distcc 3.4 x86_64-alt-linux-gnu; built Aug 26 2021 06:59:59
distcc[90365] (dcc_recursion_safeguard) safeguard level=0
distcc[90365] (main) compiler name is "distcc"
distcc[90365] (dcc_scan_args) scanning arguments: gcc -c hello.c
distcc[90365] (dcc_scan_args) found input file "hello.c"
distcc[90365] (dcc_scan_args) no visible output file, going to add "-o hello.o" at end
distcc[90365] compile from hello.c to hello.o
distcc[90365] (dcc_gcc_rewrite_fqn) Re-writing call to 'gcc' to 'x86_64-alt-linux-gcc' to support cross-compilation.
distcc[90365] (dcc_parse_hosts_file) load hosts from /home/asheplyakov/.distcc/hosts
distcc[90365] (dcc_parse_hosts) found tcp token "[fe80::216:3eff:fe66:f878%enp1s0]/20"
distcc[90365] (dcc_parse_hosts) found tcp token "[fe80::216:3eff:fea6:5c5d%enp1s0]/20"
distcc[90365] (dcc_parse_hosts) found tcp token "[fe80::216:3eff:fe9b:ed4a%enp1s0]/20"
distcc[90365] (dcc_lock_host) got cpu lock on [fe80::216:3eff:fe9b:ed4a%enp1s0]/20 slot 0 as fd3
distcc[90365] (dcc_lock_host) got cpu lock on localhost slot 0 as fd4
distcc[90365] (dcc_note_state) note state 3, file "(NULL)", host "localhost"
distcc[90365] (dcc_strip_dasho) result: x86_64-alt-linux-gcc -c hello.c
distcc[90365] (dcc_spawn_child) forking to execute: x86_64-alt-linux-gcc -E hello.c
distcc[90365] (dcc_spawn_child) child started as pid90366
distcc[90365] (dcc_strip_local_args) result: x86_64-alt-linux-gcc -c hello.c -o hello.o
distcc[90365] exec on [fe80::216:3eff:fe9b:ed4a%enp1s0]/20: x86_64-alt-linux-gcc -c hello.c -o hello.o
distcc[90365] (dcc_note_state) note state 2, file "hello.c", host "fe80::216:3eff:fe9b:ed4a%enp1s0"
distcc[90366] (dcc_new_pgrp) entered process group
distcc[90366] (dcc_increment_safeguard) setting safeguard: _DISTCC_SAFEGUARD=1
distcc[90365] (dcc_connect_by_name) ERROR: failed to look up host "fe80::216:3eff:fe9b:ed4a%enp1s0": Unknown host
distcc[90365] (dcc_unlock) release lock fd4