src: evaluate: support prefix expression in statements

Currently nft dumps core when it encounters a prefix expression as
part of a statement, e.g.
iifname ens3 snat to 10.0.0.0/28

yields:
BUG: unknown expression type prefix
nft: netlink_linearize.c:688: netlink_gen_expr: Assertion `0' failed.

This assertion is correct -- we can't linearize a prefix because
kernel doesn't know what that is.

For LHS prefixes, they get converted to a binary 'and' such as
'10.0.0.0 & 255.255.255.240'.  For RHS, we can do something similar
and convert them into a range.

snat to 10.0.0.0/28 will be converted into:
iifname "ens3" snat to 10.0.0.0-10.0.0.15

Closes: https://bugzilla.netfilter.org/show_bug.cgi?id=1187
Signed-off-by: Florian Westphal <fw@strlen.de>
Acked-by: Pablo Neira Ayuso <pablo@netfilter.org>

0 files changed, 0 insertions, 0 deletions