[ovs-dev] [PATCH] bfd: Support overlay BFD

[Yifeng Sun]

Thanks for the review. Please check my inline comments.
Will fix them in v2.

Yifeng

On Sat, Jun 27, 2020 at 3:07 PM William Tu <u9012063 at gmail.com> wrote:

> Thanks for the patch.
>
> On Wed, Jun 24, 2020 at 1:58 PM Yifeng Sun <pkusunyifeng at gmail.com> wrote:
> >
> > Current OVS intercepts and processes all BFD packets, thus VM-2-VM
> > BFD packets get lost and the recipient VM never sees them.
>
> Can you explain in more detail the issue?
> How about this below, if I understand correctly:
> "
> Currently we treat any packets coming into a BFD-enabled OVS interface
> as BFD packets for OVS,
> if they are IP, UDP, No_frag, and having BFD DEST_PORT. However, when
> consider overlay network,
> customers might deployment their own BFD protocol stack, and as a
> result, the BFD packets should be
> forwarded to the customer instead of being processed at OVS.
> "
>
>
Yes, correct.


> >
> > This patch fixes it by only intercepting and processing BFD packets
>
> maybe not "intercepting", but here we are adding additional check.
>
>
Yes, your rephrase is more accurate.


> > destined to a configured BFD instance, and other BFD packets are made
> > available to the OVS flow table for forwarding.
> >
> > This patch keeps BFD's backward compatibility.
> >
> Is there a VMware-BZ ID?
>

Yes, there is, will add it in v2.


>
> > Signed-off-by: Yifeng Sun <pkusunyifeng at gmail.com>
> > ---
> >  lib/bfd.c            | 16 +++++++++++++---
> >  vswitchd/vswitch.xml |  7 +++++++
> >  2 files changed, 20 insertions(+), 3 deletions(-)
> >
> > diff --git a/lib/bfd.c b/lib/bfd.c
> > index cc8c6857afa4..3c965699ace3 100644
> > --- a/lib/bfd.c
> > +++ b/lib/bfd.c
> > @@ -149,6 +149,9 @@ BUILD_ASSERT_DECL(BFD_PACKET_LEN == sizeof(struct
> msg));
> >  #define FLAGS_MASK 0x3f
> >  #define DEFAULT_MULT 3
> >
> > +#define BFD_DEFAULT_SRC_IP 0xA9FE0101 /* 169.254.1.1 */
> > +#define BFD_DEFAULT_DST_IP 0xA9FE0100 /* 169.254.1.0 */
> > +
> >  struct bfd {
> >      struct hmap_node node;        /* In 'all_bfds'. */
> >      uint32_t disc;                /* bfd.LocalDiscr. Key in 'all_bfds'
> hmap. */
> > @@ -457,9 +460,9 @@ bfd_configure(struct bfd *bfd, const char *name,
> const struct smap *cfg,
> >                           &bfd->rmt_eth_dst);
> >
> >      bfd_lookup_ip(smap_get_def(cfg, "bfd_src_ip", ""),
> > -                  htonl(0xA9FE0101) /* 169.254.1.1 */, &bfd->ip_src);
> > +                  htonl(BFD_DEFAULT_SRC_IP), &bfd->ip_src);
> >      bfd_lookup_ip(smap_get_def(cfg, "bfd_dst_ip", ""),
> > -                  htonl(0xA9FE0100) /* 169.254.1.0 */, &bfd->ip_dst);
> > +                  htonl(BFD_DEFAULT_DST_IP), &bfd->ip_dst);
> >
> >      forwarding_if_rx = smap_get_bool(cfg, "forwarding_if_rx", false);
> >      if (bfd->forwarding_if_rx != forwarding_if_rx) {
> > @@ -674,7 +677,14 @@ bfd_should_process_flow(const struct bfd *bfd_,
> const struct flow *flow,
> >          memset(&wc->masks.nw_proto, 0xff, sizeof wc->masks.nw_proto);
> >          if (flow->nw_proto == IPPROTO_UDP
> >              && !(flow->nw_frag & FLOW_NW_FRAG_LATER)
> > -            && tp_dst_equals(flow, BFD_DEST_PORT, wc)) {
> > +            && tp_dst_equals(flow, BFD_DEST_PORT, wc)
> > +            && (bfd->ip_src == htonl(BFD_DEFAULT_SRC_IP)
> > +                || bfd->ip_src == flow->nw_dst)) {
> > +
> > +            if (bfd->ip_src == flow->nw_dst) {
> > +                memset(&wc->masks.nw_dst, 0xffffffff, sizeof
> wc->masks.nw_dst);
> Why doing the above?
>

This is because, besides BFD port, we additionally match BFD
packet's destination address with OVS's BFD interface. Therefore, OVS won't
treat BFD packets targeted at VM as local BFD packets.

>
> btw, is it possible to add a userspace test (make check)?
>
> Good idea, will do in v2.


> Thanks,
> William
>