Merge branch 'bpf_iter_tcp_udp'

Yonghong Song says:

====================
bpf iterator implments traversal of kernel data structures and these
data structures are passed to a bpf program for processing.
This gives great flexibility for users to examine kernel data
structure without using e.g. /proc/net which has limited and
fixed format.

Commit 138d0be35b14 ("net: bpf: Add netlink and ipv6_route bpf_iter targets")
implemented bpf iterators for netlink and ipv6_route.
This patch set intends to implement bpf iterators for tcp and udp.

Currently, /proc/net/tcp is used to print tcp4 stats and /proc/net/tcp6
is used to print tcp6 stats. /proc/net/udp[6] have similar usage model.
In contrast, only one tcp iterator is implemented and it is bpf program
resposibility to filter based on socket family. The same is for udp.
This will avoid another unnecessary traversal pass if users want
to check both tcp4 and tcp6.

Several helpers are also implemented in this patch
  bpf_skc_to_{tcp, tcp6, tcp_timewait, tcp_request, udp6}_sock
The argument for these helpers is not a fixed btf_id. For example,
  bpf_skc_to_tcp(struct sock_common *), or
  bpf_skc_to_tcp(struct sock *), or
  bpf_skc_to_tcp(struct inet_sock *), ...
are all valid. At runtime, the helper will check whether pointer cast
is legal or not. Please see Patch #5 for details.

Since btf_id's for both arguments and return value are known at
build time, the btf_id's are pre-computed once vmlinux btf becomes
valid. Jiri's "adding d_path helper" patch set
  https://lore.kernel.org/bpf/20200616100512.2168860-1-jolsa@kernel.org/T/
provides a way to pre-compute btf id during vmlinux build time.
This can be applied here as well. A followup patch can convert
to build time btf id computation after Jiri's patch landed.

Changelogs:
  v4 -> v5:
    - fix bpf_skc_to_udp6_sock helper as besides sk_protocol, sk_family,
      sk_type == SOCK_DGRAM is also needed to differentiate from
      SOCK_RAW (Eric)
  v3 -> v4:
    - fix bpf_skc_to_{tcp_timewait, tcp_request}_sock helper implementation
      as just checking sk->sk_state is not enough (Martin)
    - fix a few kernel test robot reported failures
    - move bpf_tracing_net.h from libbpf to selftests (Andrii)
    - remove __weak attribute from selftests CONFIG_HZ variables (Andrii)
  v2 -> v3:
    - change sock_cast*/SOCK_CAST* names to btf_sock* names for generality (Martin)
    - change gpl_license to false (Martin)
    - fix helper to cast to tcp timewait/request socket. (Martin)
  v1 -> v2:
    - guard init_sock_cast_types() defination properly with CONFIG_NET (Martin)
    - reuse the btf_ids, computed for new helper argument, for return
      values (Martin)
    - using BTF_TYPE_EMIT to express intent of btf type generation (Andrii)
    - abstract out common net macros into bpf_tracing_net.h (Andrii)
====================

Signed-off-by: Alexei Starovoitov <ast@kernel.org>

1 files changed, 51 insertions, 0 deletions

diff --git a/tools/testing/selftests/bpf/progs/bpf_tracing_net.h b/tools/testing/selftests/bpf/progs/bpf_tracing_net.h
new file mode 100644
index 000000000000..01378911252b
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/bpf_tracing_net.h
@@ -0,0 +1,51 @@
+/* SPDX-License-Identifier: (LGPL-2.1 OR BSD-2-Clause) */
+#ifndef __BPF_TRACING_NET_H__
+#define __BPF_TRACING_NET_H__
+
+#define AF_INET			2
+#define AF_INET6		10
+
+#define ICSK_TIME_RETRANS	1
+#define ICSK_TIME_PROBE0	3
+#define ICSK_TIME_LOSS_PROBE	5
+#define ICSK_TIME_REO_TIMEOUT	6
+
+#define IFNAMSIZ		16
+
+#define RTF_GATEWAY		0x0002
+
+#define TCP_INFINITE_SSTHRESH	0x7fffffff
+#define TCP_PINGPONG_THRESH	3
+
+#define fib_nh_dev		nh_common.nhc_dev
+#define fib_nh_gw_family	nh_common.nhc_gw_family
+#define fib_nh_gw6		nh_common.nhc_gw.ipv6
+
+#define inet_daddr		sk.__sk_common.skc_daddr
+#define inet_rcv_saddr		sk.__sk_common.skc_rcv_saddr
+#define inet_dport		sk.__sk_common.skc_dport
+
+#define ir_loc_addr		req.__req_common.skc_rcv_saddr
+#define ir_num			req.__req_common.skc_num
+#define ir_rmt_addr		req.__req_common.skc_daddr
+#define ir_rmt_port		req.__req_common.skc_dport
+#define ir_v6_rmt_addr		req.__req_common.skc_v6_daddr
+#define ir_v6_loc_addr		req.__req_common.skc_v6_rcv_saddr
+
+#define sk_family		__sk_common.skc_family
+#define sk_rmem_alloc		sk_backlog.rmem_alloc
+#define sk_refcnt		__sk_common.skc_refcnt
+#define sk_state		__sk_common.skc_state
+#define sk_v6_daddr		__sk_common.skc_v6_daddr
+#define sk_v6_rcv_saddr		__sk_common.skc_v6_rcv_saddr
+
+#define s6_addr32		in6_u.u6_addr32
+
+#define tw_daddr		__tw_common.skc_daddr
+#define tw_rcv_saddr		__tw_common.skc_rcv_saddr
+#define tw_dport		__tw_common.skc_dport
+#define tw_refcnt		__tw_common.skc_refcnt
+#define tw_v6_daddr		__tw_common.skc_v6_daddr
+#define tw_v6_rcv_saddr		__tw_common.skc_v6_rcv_saddr
+
+#endif