call, emit, match: Add support for vectorised operations, nfnetlinkHEADmaster

We want to add and delete rules with iptables(8), and manipulate set
elements with nft(8).

These are the first users we encounter sending multiple netlink
messages in one sendmsg().

To support matching on those, we need to iterate over several
messages, looking for a matching one, or a mismatching one (depending
on quantifiers and match type), but we don't want to implement program
loops because of security design reasons.

We can't implement a generalised instruction that vectorises existing
ones, either, because we need to support universal and existential
quantifiers in fields that are repeated multiple times, once per each
netlink message, with bitwise operations and non-exact matching types.

Add vectorisation support to OP_CMP and OP_BITWISE instead, with a
generic description for a vector (only sequences of netlink messages
with length in nlmsghdr are supported at the moment) so that,
depending on the quantifiers, we'll repeat those operations as many
times as needed. This way, we don't risk any O(n^2) explosion, and we
are bound by O(m * n) instead, with m compare/bitwise operations for
a given expression, and n number of netlink messages.

Add demos for nft and iptables using the new concepts.

Signed-off-by: Stefano Brivio <sbrivio@redhat.com>

1 files changed, 8 insertions, 0 deletions

diff --git a/common/gluten.h b/common/gluten.h
index d06362a..4e1c249 100644
--- a/common/gluten.h
+++ b/common/gluten.h
@@ -222,6 +222,12 @@ struct op_iovload {
 	struct gluten_offset iovlen;
 	struct gluten_offset dst;
 	size_t size;
+	size_t zero_fill;
+};
+
+struct vec_desc {
+	struct gluten_offset start;
+	off_t len_offset;
 };
 
 enum op_cmp_type {
@@ -238,6 +244,7 @@ extern const char *cmp_type_str[CMP_MAX + 1];
 struct cmp_desc {
 	enum op_cmp_type cmp;
 	size_t size;
+	struct vec_desc vec;
 	struct gluten_offset x;
 	struct gluten_offset y;
 	struct gluten_offset jmp;
@@ -258,6 +265,7 @@ extern const char *bitwise_type_str[BITWISE_MAX + 1];
 struct bitwise_desc {
 	size_t size;
 	enum bitwise_type type;
+	struct vec_desc vec;
 	struct gluten_offset dst;
 	struct gluten_offset x;
 	struct gluten_offset y;