libxtables: Fix for warning in xtables_ipmask_to_numeric

Gcc complains:

| xtables.c: In function 'xtables_ipmask_to_numeric':
| xtables.c:1491:34: warning: '__builtin___sprintf_chk' may write a terminating nul past the end of the destination [-Wformat-overflow=]
|  1491 |                 sprintf(buf, "/%s", xtables_ipaddr_to_numeric(mask));
|       |                                  ^

Indeed, xtables_ipaddr_to_numeric() returns a pointer to a 20 byte
buffer and xtables_ipmask_to_numeric() writes its content into a buffer
of same size at offset 1. Yet length of returned string is deterministic
as it is an IPv4 address. So shrink it to the minimum of 16 bytes which
eliminates the warning as well.

Fixes: a96166c24eaac ("libxtables: add xtables_ip[6]mask_to_cidr")
Signed-off-by: Phil Sutter <phil@nwl.cc>

0 files changed, 0 insertions, 0 deletions