Re: [PATCHv5 bpf-next 1/3] xdp: add a new helper for dev map multicast support

On Tue, Jun 30, 2020 at 9:21 PM Hangbin Liu [off-list ref] wrote:

This patch is for xdp multicast support. In this implementation we
add a new helper to accept two maps: forward map and exclude map.
We will redirect the packet to all the interfaces in *forward map*, but
exclude the interfaces that in *exclude map*.

To achive this I add a new ex_map for struct bpf_redirect_info.
in the helper I set tgt_value to NULL to make a difference with
bpf_xdp_redirect_map()

We also add a flag *BPF_F_EXCLUDE_INGRESS* incase you don't want to
create a exclude map for each interface and just want to exclude the
ingress interface.

The general data path is kept in net/core/filter.c. The native data
path is in kernel/bpf/devmap.c so we can use direct calls to
get better performace.

v5:
a) Check devmap_get_next_key() return value.
b) Pass through flags to __bpf_tx_xdp_map() instead of bool value.
c) In function dev_map_enqueue_multi(), consume xdpf for the last
   obj instead of the first on.
d) Update helper description and code comments to explain that we
   use NULL target value to distinguish multicast and unicast
   forwarding.
e) Update memory model, memory id and frame_sz in xdpf_clone().

v4: Fix bpf_xdp_redirect_map_multi_proto arg2_type typo

v3: Based on Toke's suggestion, do the following update
a) Update bpf_redirect_map_multi() description in bpf.h.
b) Fix exclude_ifindex checking order in dev_in_exclude_map().
c) Fix one more xdpf clone in dev_map_enqueue_multi().
d) Go find next one in dev_map_enqueue_multi() if the interface is not
   able to forward instead of abort the whole loop.
e) Remove READ_ONCE/WRITE_ONCE for ex_map.

v2: Add new syscall bpf_xdp_redirect_map_multi() which could accept
include/exclude maps directly.

Signed-off-by: Hangbin Liu <redacted>
---
 include/linux/bpf.h            |  20 +++++
 include/linux/filter.h         |   1 +
 include/net/xdp.h              |   1 +
 include/uapi/linux/bpf.h       |  25 +++++-
 kernel/bpf/devmap.c            | 154 +++++++++++++++++++++++++++++++++
 kernel/bpf/verifier.c          |   6 ++
 net/core/filter.c              | 109 +++++++++++++++++++++--
 net/core/xdp.c                 |  29 +++++++
 tools/include/uapi/linux/bpf.h |  25 +++++-
 9 files changed, 363 insertions(+), 7 deletions(-)

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We've recently converted all return types for helpers from int to
long, please update accordingly. Thanks.

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