src: add dynamic register allocation infrastructure

Starting Linux kernel 5.18-rc, operations on registers that already
contain the expected data are turned into noop.

Track operation on registers to use the same register through
nftnl_reg_get(). This patch introduces an LRU eviction strategy when all
the registers are in used.

nftnl_reg_get_scratch() is used to allocate a register as scratchpad
area: no tracking is performed in this case, although register eviction
might occur.

Acked-by: Phil Sutter <phil@nwl.cc>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

1 files changed, 7 insertions, 0 deletions

diff --git a/src/libnftnl.map b/src/libnftnl.map
index ad8f2af..3a85325 100644
--- a/src/libnftnl.map
+++ b/src/libnftnl.map
@@ -387,3 +387,10 @@ LIBNFTNL_16 {
 LIBNFTNL_17 {
   nftnl_set_elem_nlmsg_build;
 } LIBNFTNL_16;
+
+LIBNFTNL_18 {
+  nftnl_regs_alloc;
+  nftnl_regs_free;
+  nftnl_reg_get;
+  nftnl_reg_get_scratch;
+} LIBNFTNL_17;