xfrm: configure policy hash table thresholds by netlink

Enable to specify local and remote prefix length thresholds for the
policy hash table via a netlink XFRM_MSG_NEWSPDINFO message.

prefix length thresholds are specified by XFRMA_SPD_IPV4_HTHRESH and
XFRMA_SPD_IPV6_HTHRESH optional attributes (struct xfrmu_spdhthresh).

example:

    struct xfrmu_spdhthresh thresh4 = {
        .lbits = 0;
        .rbits = 24;
    };
    struct xfrmu_spdhthresh thresh6 = {
        .lbits = 0;
        .rbits = 56;
    };
    struct nlmsghdr *hdr;
    struct nl_msg *msg;

    msg = nlmsg_alloc();
    hdr = nlmsg_put(msg, NL_AUTO_PORT, NL_AUTO_SEQ, XFRMA_SPD_IPV4_HTHRESH, sizeof(__u32), NLM_F_REQUEST);
    nla_put(msg, XFRMA_SPD_IPV4_HTHRESH, sizeof(thresh4), &thresh4);
    nla_put(msg, XFRMA_SPD_IPV6_HTHRESH, sizeof(thresh6), &thresh6);
    nla_send_auto(sk, msg);

The numbers are the policy selector minimum prefix lengths to put a
policy in the hash table.

- lbits is the local threshold (source address for out policies,
  destination address for in and fwd policies).

- rbits is the remote threshold (destination address for out
  policies, source address for in and fwd policies).

The default values are:

XFRMA_SPD_IPV4_HTHRESH: 32 32
XFRMA_SPD_IPV6_HTHRESH: 128 128

Dynamic re-building of the SPD is performed when the thresholds values
are changed.

The current thresholds can be read via a XFRM_MSG_GETSPDINFO request:
the kernel replies to XFRM_MSG_GETSPDINFO requests by an
XFRM_MSG_NEWSPDINFO message, with both attributes
XFRMA_SPD_IPV4_HTHRESH and XFRMA_SPD_IPV6_HTHRESH.

Signed-off-by: Christophe Gouault <christophe.gouault@6wind.com>
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>

1 files changed, 7 insertions, 0 deletions

diff --git a/include/uapi/linux/xfrm.h b/include/uapi/linux/xfrm.h
index 25e5dd916ba4..02d5125a5ee8 100644
--- a/include/uapi/linux/xfrm.h
+++ b/include/uapi/linux/xfrm.h
@@ -328,6 +328,8 @@ enum xfrm_spdattr_type_t {
         XFRMA_SPD_UNSPEC,
         XFRMA_SPD_INFO,
         XFRMA_SPD_HINFO,
+        XFRMA_SPD_IPV4_HTHRESH,
+        XFRMA_SPD_IPV6_HTHRESH,
         __XFRMA_SPD_MAX
 
 #define XFRMA_SPD_MAX (__XFRMA_SPD_MAX - 1)
@@ -347,6 +349,11 @@ struct xfrmu_spdhinfo {
         __u32 spdhmcnt;
 };
 
+struct xfrmu_spdhthresh {
+        __u8 lbits;
+        __u8 rbits;
+};
+
 struct xfrm_usersa_info {
         struct xfrm_selector            sel;
         struct xfrm_id                  id;