[RFC v2 PATCH 0/4] eBPF and struct scatterlist

[Tushar Dave <tushar.n.dave@oracle.com>]

This follows up on https://patchwork.ozlabs.org/cover/927050/
where the review feedback was to use bpf_skb_load_bytes() to deal with
linear and non-linear skbs. While that feedback is valid and correct,
the motivation for this work is to allow eBPF based firewalling for
kernel modules that do not always get their packet as an sk_buff from
their downlink drivers. One such instance of this use-case is RDS, which
can be run both over IB (driver RDMA's a scatterlist to the RDS module)
or over TCP (TCP passes an sk_buff to the RDS module)

This RFC (call it v2) uses exiting socket filter infrastructure and
extend it with new eBPF program type that deals with struct scatterlist.
For RDS, the integrated approach treats the scatterlist as the common
denominator, and allows the application to write a filter for processing
a scatterlist.


Details:
Patch 1 adds new eBPF prog type BPF_PROG_TYPE_SOCKET_SG_FILTER which
uses the existing socket filter infrastructure for bpf program attach
and load. eBPF program of type BPF_PROG_TYPE_SOCKET_SG_FILTER receives
struct scatterlist as bpf context contrast to
BPF_PROG_TYPE_SOCKET_FILTER which deals with struct skb. This new eBPF
program type allow socket filter to run on packet data that is in form
form of struct scatterlist.

Patch 2 adds functionality to run BPF_PROG_TYPE_SOCKET_SG_FILTER socket
filter program. A bpf helpers bpf_sg_next() is also added so users can
retrieve sg elements from scatterlist.

Patch 3 adds socket filter eBPF sample program that uses patch 1 and
patch 2. The sample program opens an rds socket, attach ebpf program
(socksg i.e. BPF_PROG_TYPE_SOCKET_SG_FILTER) to rds socket and uses
bpf_sg_next helper to look into sg. For a test, current ebpf program
only prints first few bytes from each elements of sg list.

Finally, patch 4 allows rds_recv_incoming to invoke socket filter
program which deals with scatterlist.

Thanks.

-Tushar

Tushar Dave (4):
  eBPF: Add new eBPF prog type BPF_PROG_TYPE_SOCKET_SG_FILTER
  ebpf: Add sg_filter_run and sg helper
  ebpf: Add sample ebpf program for SOCKET_SG_FILTER
  rds: invoke socket sg filter attached to rds socket

 include/linux/bpf_types.h                 |   1 +
 include/linux/filter.h                    |  10 +
 include/uapi/linux/bpf.h                  |  17 +-
 kernel/bpf/syscall.c                      |   1 +
 kernel/bpf/verifier.c                     |   1 +
 net/core/filter.c                         | 149 ++++++++++++-
 net/rds/ib.c                              |   1 +
 net/rds/ib.h                              |   1 +
 net/rds/ib_recv.c                         |  12 ++
 net/rds/rds.h                             |   2 +
 net/rds/recv.c                            |  16 ++
 net/rds/tcp.c                             |   2 +
 net/rds/tcp.h                             |   2 +
 net/rds/tcp_recv.c                        |  38 ++++
 samples/bpf/Makefile                      |   3 +
 samples/bpf/bpf_load.c                    |  11 +-
 samples/bpf/rds_filter_kern.c             |  78 +++++++
 samples/bpf/rds_filter_user.c             | 339 ++++++++++++++++++++++++++++++
 tools/bpf/bpftool/prog.c                  |   1 +
 tools/include/uapi/linux/bpf.h            |  17 +-
 tools/lib/bpf/libbpf.c                    |   3 +
 tools/lib/bpf/libbpf.h                    |   2 +
 tools/testing/selftests/bpf/bpf_helpers.h |   3 +
 23 files changed, 703 insertions(+), 7 deletions(-)
 create mode 100644 samples/bpf/rds_filter_kern.c
 create mode 100644 samples/bpf/rds_filter_user.c

-- 
1.8.3.1