payload: only merge if adjacent and combined size fits into a register

add rule ip6 filter input ip6 saddr ::1/128 ip6 daddr ::1/128 fails,
we ask to compare a 32byte immediate which is not supported:

  [ payload load 32b @ network header + 8 => reg 1 ]
  [ cmp eq reg 1 0x00000000 0x00000000 0x00000000 0x01000000 0x00000000 0x00000000 0x00000000 0x02000000 ]

We would need to use two cmps in this case, i.e.:

  [ payload load 32b @ network header + 8 => reg 1 ]
  [ cmp eq reg 1 0x00000000 0x00000000 0x00000000 0x01000000 ]
  [ cmp eq reg 2 0x00000000 0x00000000 0x00000000 0x02000000 ]

Seems however that this requires a bit more changes to how nft
handles register allocations, we'd also need to undo the constant merge.

Lets disable merging for now so that we generate

  [ payload load 16b @ network header + 8 => reg 1 ]
  [ cmp eq reg 1 0x00000000 0x00000000 0x00000000 0x01000000 ]
  [ payload load 16b @ network header + 24 => reg 1 ]
  [ cmp eq reg 1 0x00000000 0x00000000 0x00000000 0x02000000 ]

... if merge would bring us over the 128 bit register size.

Closes: http://bugzilla.netfilter.org/show_bug.cgi?id=1032
Signed-off-by: Florian Westphal <fw@strlen.de>
Acked-by: Arturo Borrero Gonzalez <arturo.borrero.glez@gmail.com>
Acked-by: Pablo Neira Ayuso <pablo@netfilter.org>

1 files changed, 1 insertions, 1 deletions

diff --git a/src/rule.c b/src/rule.c
index b7f4a07f..2fe67454 100644
--- a/src/rule.c
+++ b/src/rule.c
@@ -1292,7 +1292,7 @@ static void payload_do_merge(struct stmt *sa[], unsigned int n)
 		stmt = sa[i];
 		this = stmt->expr;
 
-		if (!payload_is_adjacent(last->left, this->left) ||
+		if (!payload_can_merge(last->left, this->left) ||
 		    last->op != this->op) {
 			last = this;
 			j = i;