[iptables PATCH 2/3] arptables: Fix --proto-type mask formatting

[Phil Sutter <phil@nwl.cc>]

Arptables accepts numeric --proto-type values and masks in any numeral
system identified by (absence of) prefix. Yet it prints the mask value
in hex without '0x'-prefix, breaking save and restore the same way
numeric --h-type output did.

In theory, this could be fixed either by adding the missing prefix or
printing the mask in decimal (like most other builtin matches do), but
since the value is printed in hex with prefix already, align mask output
with that.

Also a day 1 bug and consistent with legacy, so no Fixes: tag here as
well.

Signed-off-by: Phil Sutter <phil@nwl.cc>
---
 extensions/libarpt_standard.t | 4 ++++
 iptables/nft-arp.c            | 2 +-
 2 files changed, 5 insertions(+), 1 deletion(-)

diff --git a/extensions/libarpt_standard.t b/extensions/libarpt_standard.t
index a2b0a36a4a6bf..b9a3560660372 100644
--- a/extensions/libarpt_standard.t
+++ b/extensions/libarpt_standard.t
@@ -16,3 +16,7 @@
 --src-mac ! 01:02:03:04:05:06 --dst-mac ! 07:08:09:0A:0B:0C --h-length ! 6 --opcode ! Request --h-type ! Ethernet --proto-type ! ipv4;! --src-mac 01:02:03:04:05:06 ! --dst-mac 07:08:09:0a:0b:0c ! --h-length 6 ! --opcode 1 ! --h-type 0x1 ! --proto-type 0x800;OK
 --h-type 10;--h-type 0x10;OK
 --h-type 0x10;=;OK
+--proto-type 10;--proto-type 0xa;OK
+--proto-type 10/10;--proto-type 0xa/0xa;OK
+--proto-type 0x10;=;OK
+--proto-type 0x10/0x10;=;OK
diff --git a/iptables/nft-arp.c b/iptables/nft-arp.c
index 83aec5003004e..38b2ab3993128 100644
--- a/iptables/nft-arp.c
+++ b/iptables/nft-arp.c
@@ -339,7 +339,7 @@ static void nft_arp_print_rule_details(const struct iptables_command_state *cs,
 		else
 			printf("--proto-type 0x%x", tmp);
 		if (fw->arp.arpro_mask != 65535)
-			printf("/%x", ntohs(fw->arp.arpro_mask));
+			printf("/0x%x", ntohs(fw->arp.arpro_mask));
 		sep = " ";
 	}
 }
-- 
2.41.0