$ # FIXED-KERNEL VALIDATION (kernel #1 Fri Sep 11 09:08:32, fix.diff applied)
$ vmstat -m | grep routetbl
           routetbl     234   38.0K       0    390M      283
$ # unpriv (uid 1001) unique-genmask PoC:
/tmp/rtmask_poc 100000; echo POC_EXIT=$?
iter 0: unexpected errno 1 (Operation not permitted)      <- EPERM, as fixed
POC_EXIT=1
$ vmstat -m | grep routetbl
           routetbl     234   38.0K       0    390M      284   <- ZERO growth

$ # positive control 1: root can still install genmasks (10k unique):
/tmp/rtmask_poc 10000   # as root
ROOT_POC_EXIT=0
$ vmstat -m | grep routetbl
           routetbl    58.8K    7.36M       0    390M    68.6K  <- +6/cpu/msg intact

$ # positive control 2: unprivileged plain RTM_GET (no genmask) unaffected:
/tmp/rtget_plain          # as uid 1001
write=168 errno=0 (Undefined error: 0)
RC=0                      <- not EPERM: route(8)-style monitors still work