Re: [PATCH net-next 2/2] net: ipv6: ioam6: new feature tunsrc

[Justin Iurman]

On 8/13/24 13:06, Paolo Abeni wrote:
> On 8/9/24 14:39, Justin Iurman wrote:
> > This patch provides a new feature (i.e., "tunsrc") for the tunnel (i.e.,
> > "encap") mode of ioam6. Just like seg6 already does, except it is
> > attached to a route. The "tunsrc" is optional: when not provided (by
> > default), the automatic resolution is applied. Using "tunsrc" when
> > possible has a benefit: performance.
>
> It's customary to include performances figures in performance related 
> changeset ;)

Indeed, I realized it too late... thx for the reminder!

Before (= "encap" mode): https://ibb.co/bNCzvf7
After (= "encap" mode with "tunsrc"): https://ibb.co/PT8L6yq

I'll add these again to -v2.

> > Signed-off-by: Justin Iurman <justin.iurman@xxxxxxxxx>
> > ---
> >   include/uapi/linux/ioam6_iptunnel.h |  7 +++++
> >   net/ipv6/ioam6_iptunnel.c           | 48 ++++++++++++++++++++++++++---
> >   2 files changed, 51 insertions(+), 4 deletions(-)
> >
> > diff --git a/include/uapi/linux/ioam6_iptunnel.h 
> > b/include/uapi/linux/ioam6_iptunnel.h
> > index 38f6a8fdfd34..6cdbd0da7ad8 100644
> > --- a/include/uapi/linux/ioam6_iptunnel.h
> > +++ b/include/uapi/linux/ioam6_iptunnel.h
> > @@ -50,6 +50,13 @@ enum {
> >       IOAM6_IPTUNNEL_FREQ_K,        /* u32 */
> >       IOAM6_IPTUNNEL_FREQ_N,        /* u32 */
> > +    /* Tunnel src address.
> > +     * For encap,auto modes.
> > +     * Optional (automatic if
> > +     * not provided).
> > +     */
> > +    IOAM6_IPTUNNEL_SRC,        /* struct in6_addr */
> > +
> >       __IOAM6_IPTUNNEL_MAX,
> >   };
> > diff --git a/net/ipv6/ioam6_iptunnel.c b/net/ipv6/ioam6_iptunnel.c
> > index cd2522f04edf..e0e73faf9969 100644
> > --- a/net/ipv6/ioam6_iptunnel.c
> > +++ b/net/ipv6/ioam6_iptunnel.c
> > @@ -42,6 +42,8 @@ struct ioam6_lwt {
> >       struct ioam6_lwt_freq freq;
> >       atomic_t pkt_cnt;
> >       u8 mode;
> > +    bool has_tunsrc;
> > +    struct in6_addr tunsrc;
> >       struct in6_addr tundst;
> >       struct ioam6_lwt_encap tuninfo;
> >   };
> > @@ -72,6 +74,7 @@ static const struct nla_policy 
> > ioam6_iptunnel_policy[IOAM6_IPTUNNEL_MAX + 1] = {
> >       [IOAM6_IPTUNNEL_MODE]    = NLA_POLICY_RANGE(NLA_U8,
> >                              IOAM6_IPTUNNEL_MODE_MIN,
> >                              IOAM6_IPTUNNEL_MODE_MAX),
> > +    [IOAM6_IPTUNNEL_SRC]    = NLA_POLICY_EXACT_LEN(sizeof(struct 
> > in6_addr)),
> >       [IOAM6_IPTUNNEL_DST]    = NLA_POLICY_EXACT_LEN(sizeof(struct 
> > in6_addr)),
> >       [IOAM6_IPTUNNEL_TRACE]    = NLA_POLICY_EXACT_LEN(
> >                       sizeof(struct ioam6_trace_hdr)),
> > @@ -144,6 +147,11 @@ static int ioam6_build_state(struct net *net, 
> > struct nlattr *nla,
> >       else
> >           mode = nla_get_u8(tb[IOAM6_IPTUNNEL_MODE]);
> > +    if (tb[IOAM6_IPTUNNEL_SRC] && mode == IOAM6_IPTUNNEL_MODE_INLINE) {
> > +        NL_SET_ERR_MSG(extack, "no tunnel source expected in this 
> > mode");
> > +        return -EINVAL;
> > +    }
>
> when mode is IOAM6_IPTUNNEL_MODE_AUTO, the data path could still add the 
> encapsulation for forwarded packets, why explicitly preventing this 
> optimization in such scenario?

Good catch! I guess we can just ignore "tunsrc" if provided with inline 
mode, instead of returning an error.

> > +
> >       if (!tb[IOAM6_IPTUNNEL_DST] && mode != 
> > IOAM6_IPTUNNEL_MODE_INLINE) {
> >           NL_SET_ERR_MSG(extack, "this mode needs a tunnel destination");
> >           return -EINVAL;
> > @@ -178,6 +186,14 @@ static int ioam6_build_state(struct net *net, 
> > struct nlattr *nla,
> >       ilwt->freq.n = freq_n;
> >       ilwt->mode = mode;
> > +
> > +    if (!tb[IOAM6_IPTUNNEL_SRC]) {
> > +        ilwt->has_tunsrc = false;
> > +    } else {
> > +        ilwt->has_tunsrc = true;
> > +        ilwt->tunsrc = nla_get_in6_addr(tb[IOAM6_IPTUNNEL_SRC]);
>
> Since you are going to use the source address only if != ANY, I think it 
> would be cleaner to refuse such addresses here. That will avoid an 
> additional check in the datapath.

+1.

Thanks,
Justin

> Cheers,
>
> Paolo