Re: [PATCH net-next v4 4/5] ipv6: ioam: Support for IOAM injection with lwtunnels

On Thu, 27 May 2021 17:16:51 +0200 Justin Iurman wrote:

Add support for the IOAM inline insertion (only for the host-to-host use case)
which is per-route configured with lightweight tunnels. The target is iproute2
and the patch is ready. It will be posted as soon as this patchset is merged.
Here is an overview:

$ ip -6 ro ad fc00::1/128 encap ioam6 trace type 0x800000 ns 1 size 12 dev eth0

This example configures an IOAM Pre-allocated Trace option attached to the
fc00::1/128 prefix. The IOAM namespace (ns) is 1, the size of the pre-allocated
trace data block is 12 octets (size) and only the first IOAM data (bit 0:
hop_limit + node id) is included in the trace (type) represented as a bitfield.

The reason why the in-transit (IPv6-in-IPv6 encapsulation) use case is not
implemented is explained on the patchset cover.

Signed-off-by: Justin Iurman <redacted>

+static const struct nla_policy ioam6_iptunnel_policy[IOAM6_IPTUNNEL_MAX + 1] = {
+	[IOAM6_IPTUNNEL_TRACE]	= { .type = NLA_BINARY },

Please use NLA_POLICY_EXACT_LEN(sizeof(..)), that should avoid the need
for explicit check in the code.

+};

+static int ioam6_build_state(struct net *net, struct nlattr *nla,
+			     unsigned int family, const void *cfg,
+			     struct lwtunnel_state **ts,
+			     struct netlink_ext_ack *extack)
+{
+	struct nlattr *tb[IOAM6_IPTUNNEL_MAX + 1];
+	struct ioam6_lwt_encap *tuninfo;
+	struct ioam6_trace_hdr *trace;
+	struct lwtunnel_state *s;
+	int len_aligned;
+	int len, err;
+
+	if (family != AF_INET6)
+		return -EINVAL;
+
+	err = nla_parse_nested(tb, IOAM6_IPTUNNEL_MAX, nla,
+			       ioam6_iptunnel_policy, extack);
+	if (err < 0)
+		return err;
+
+	if (!tb[IOAM6_IPTUNNEL_TRACE])
+		return -EINVAL;
+
+	trace = nla_data(tb[IOAM6_IPTUNNEL_TRACE]);
+	if (nla_len(tb[IOAM6_IPTUNNEL_TRACE]) != sizeof(*trace))
+		return -EINVAL;
+
+	if (!ioam6_validate_trace_hdr(trace))
+		return -EINVAL;

It'd be good to set the extack message and attribute here. And perhaps
a message for the case of trace missing.

+	len = sizeof(*tuninfo) + trace->remlen * 4;
+	len_aligned = ALIGN(len, 8);