On Sat, Aug 3, 2019 at 8:29 PM Farid Zakaria <farid.m.zakaria@xxxxxxxxx> wrote:
>
> Foo over UDP uses UDP encapsulation to add additional entropy
> into the packets so that they get beter distribution across EMCP
> routes.
>
> Expose udp_flow_src_port as a bpf helper so that tunnel filters
> can benefit from the helper.
>
> Signed-off-by: Farid Zakaria <farid.m.zakaria@xxxxxxxxx>
> ---
> include/uapi/linux/bpf.h | 21 +++++++--
> net/core/filter.c | 20 ++++++++
> tools/include/uapi/linux/bpf.h | 21 +++++++--
> tools/testing/selftests/bpf/bpf_helpers.h | 2 +
> .../bpf/prog_tests/udp_flow_src_port.c | 28 +++++++++++
> .../bpf/progs/test_udp_flow_src_port_kern.c | 47 +++++++++++++++++++
> 6 files changed, 131 insertions(+), 8 deletions(-)
> create mode 100644 tools/testing/selftests/bpf/prog_tests/udp_flow_src_port.c
> create mode 100644 tools/testing/selftests/bpf/progs/test_udp_flow_src_port_kern.c
First, for each review, backport and sync with libbpf repo, in the future,
could you break the patch to two patches?
1. kernel changes (net/core/filter.c, include/uapi/linux/bpf.h)
2. tools/include/uapi/linux/bpf.h
3. tools/testing/ changes
Second, could you explain why existing __sk_buff->hash not enough?
there are corner cases where if __sk_buff->hash is 0 and the kernel did some
additional hashing, but maybe you can approximate in bpf program?
For case, min >= max, I suppose you can get min/max port values
from the user space for a particular net device and then calculate
the hash in the bpf program?
What I want to know if how much accuracy you will lose if you just
use __sk_buff->hash and do approximation in bpf program.
>
> diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
> index 4393bd4b2419..90e814153dec 100644
> --- a/include/uapi/linux/bpf.h
> +++ b/include/uapi/linux/bpf.h
> @@ -2545,9 +2545,21 @@ union bpf_attr {
> * *th* points to the start of the TCP header, while *th_len*
> * contains **sizeof**\ (**struct tcphdr**).
> *
> - * Return
> - * 0 if *iph* and *th* are a valid SYN cookie ACK, or a negative
> - * error otherwise.
> + * Return
> + * 0 if *iph* and *th* are a valid SYN cookie ACK, or a negative
> + * error otherwise.
> + *
> + * int bpf_udp_flow_src_port(struct sk_buff *skb, int min, int max, int use_eth)
> + * Description
> + * It's common to implement tunnelling inside a UDP protocol to provide
> + * additional randomness to the packet. The destination port of the UDP
> + * header indicates the inner packet type whereas the source port is used
> + * for additional entropy.
> + *
> + * Return
> + * An obfuscated hash of the packet that falls within the
> + * min & max port range.
> + * If min >= max, the default port range is used
> *
> * int bpf_sysctl_get_name(struct bpf_sysctl *ctx, char *buf, size_t buf_len, u64 flags)
> * Description
> @@ -2853,7 +2865,8 @@ union bpf_attr {
> FN(sk_storage_get), \
> FN(sk_storage_delete), \
> FN(send_signal), \
> - FN(tcp_gen_syncookie),
> + FN(tcp_gen_syncookie), \
> + FN(udp_flow_src_port),
>
> /* integer value in 'imm' field of BPF_CALL instruction selects which helper
> * function eBPF program intends to call
> diff --git a/net/core/filter.c b/net/core/filter.c
> index 5a2707918629..fdf0ebb8c2c8 100644
> --- a/net/core/filter.c
> +++ b/net/core/filter.c
> @@ -2341,6 +2341,24 @@ static const struct bpf_func_proto bpf_msg_pull_data_proto = {
> .arg4_type = ARG_ANYTHING,
> };
>
> +BPF_CALL_4(bpf_udp_flow_src_port, struct sk_buff *, skb, int, min,
> + int, max, int, use_eth)
> +{
> + struct net *net = dev_net(skb->dev);
> +
> + return udp_flow_src_port(net, skb, min, max, use_eth);
> +}
> +
[...]
