selftests/bpf: Implement sample udp/udp6 bpf_iter programs

On my VM, I got identical results between /proc/net/udp[6] and
the udp{4,6} bpf iterator.

For udp6:
  $ cat /sys/fs/bpf/p1
    sl  local_address                         remote_address                        st tx_queue rx_queue tr tm->when retrnsmt   uid  timeout inode ref pointer drops
   1405: 000080FE00000000FF7CC4D0D9EFE4FE:0222 00000000000000000000000000000000:0000 07 00000000:00000000 00:00000000 00000000   193        0 19183 2 0000000029eab111 0
  $ cat /proc/net/udp6
    sl  local_address                         remote_address                        st tx_queue rx_queue tr tm->when retrnsmt   uid  timeout inode ref pointer drops
   1405: 000080FE00000000FF7CC4D0D9EFE4FE:0222 00000000000000000000000000000000:0000 07 00000000:00000000 00:00000000 00000000   193        0 19183 2 0000000029eab111 0

For udp4:
  $ cat /sys/fs/bpf/p4
    sl  local_address rem_address   st tx_queue rx_queue tr tm->when retrnsmt   uid  timeout inode ref pointer drops
   2007: 00000000:1F90 00000000:0000 07 00000000:00000000 00:00000000 00000000     0        0 72540 2 000000004ede477a 0
  $ cat /proc/net/udp
    sl  local_address rem_address   st tx_queue rx_queue tr tm->when retrnsmt   uid  timeout inode ref pointer drops
   2007: 00000000:1F90 00000000:0000 07 00000000:00000000 00:00000000 00000000     0        0 72540 2 000000004ede477a 0
Signed-off-by: Yonghong Song <yhs@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Acked-by: Martin KaFai Lau <kafai@fb.com>
Link: https://lore.kernel.org/bpf/20200623230822.3989299-1-yhs@fb.com

tools/testing/selftests/bpf/progs/bpf_iter.h

@@ -9,6 +9,8 @@
 #define bpf_iter__task_file bpf_iter__task_file___not_used
 #define bpf_iter__tcp bpf_iter__tcp___not_used
 #define tcp6_sock tcp6_sock___not_used
+#define bpf_iter__udp bpf_iter__udp___not_used
+#define udp6_sock udp6_sock___not_used
 #include "vmlinux.h"
 #undef bpf_iter_meta
 #undef bpf_iter__bpf_map
@@ -18,6 +20,8 @@
 #undef bpf_iter__task_file
 #undef bpf_iter__tcp
 #undef tcp6_sock
+#undef bpf_iter__udp
+#undef udp6_sock
 
 struct bpf_iter_meta {
 	struct seq_file *seq;
@@ -62,3 +66,15 @@ struct tcp6_sock {
 	struct tcp_sock	tcp;
 	struct ipv6_pinfo inet6;
 } __attribute__((preserve_access_index));
+
+struct bpf_iter__udp {
+	struct bpf_iter_meta *meta;
+	struct udp_sock *udp_sk;
+	uid_t uid __attribute__((aligned(8)));
+	int bucket __attribute__((aligned(8)));
+} __attribute__((preserve_access_index));
+
+struct udp6_sock {
+	struct udp_sock	udp;
+	struct ipv6_pinfo inet6;
+} __attribute__((preserve_access_index));

tools/testing/selftests/bpf/progs/bpf_iter_udp4.c

+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2020 Facebook */
+#include "bpf_iter.h"
+#include "bpf_tracing_net.h"
+#include <bpf/bpf_helpers.h>
+#include <bpf/bpf_tracing.h>
+#include <bpf/bpf_endian.h>
+
+char _license[] SEC("license") = "GPL";
+
+static long sock_i_ino(const struct sock *sk)
+{
+	const struct socket *sk_socket = sk->sk_socket;
+	const struct inode *inode;
+	unsigned long ino;
+
+	if (!sk_socket)
+		return 0;
+
+	inode = &container_of(sk_socket, struct socket_alloc, socket)->vfs_inode;
+	bpf_probe_read(&ino, sizeof(ino), &inode->i_ino);
+	return ino;
+}
+
+SEC("iter/udp")
+int dump_udp4(struct bpf_iter__udp *ctx)
+{
+	struct seq_file *seq = ctx->meta->seq;
+	struct udp_sock *udp_sk = ctx->udp_sk;
+	struct inet_sock *inet;
+	__u16 srcp, destp;
+	__be32 dest, src;
+	__u32 seq_num;
+	int rqueue;
+
+	if (udp_sk == (void *)0)
+		return 0;
+
+	seq_num = ctx->meta->seq_num;
+	if (seq_num == 0)
+		BPF_SEQ_PRINTF(seq,
+			       "  sl  local_address rem_address   st tx_queue "
+			       "rx_queue tr tm->when retrnsmt   uid  timeout "
+			       "inode ref pointer drops\n");
+
+	/* filter out udp6 sockets */
+	inet = &udp_sk->inet;
+	if (inet->sk.sk_family == AF_INET6)
+		return 0;
+
+	inet = &udp_sk->inet;
+	dest = inet->inet_daddr;
+	src = inet->inet_rcv_saddr;
+	srcp = bpf_ntohs(inet->inet_sport);
+	destp = bpf_ntohs(inet->inet_dport);
+	rqueue = inet->sk.sk_rmem_alloc.counter - udp_sk->forward_deficit;
+
+	BPF_SEQ_PRINTF(seq, "%5d: %08X:%04X %08X:%04X ",
+		       ctx->bucket, src, srcp, dest, destp);
+
+	BPF_SEQ_PRINTF(seq, "%02X %08X:%08X %02X:%08lX %08X %5u %8d %lu %d %pK %u\n",
+		       inet->sk.sk_state,
+		       inet->sk.sk_wmem_alloc.refs.counter - 1,
+		       rqueue,
+		       0, 0L, 0, ctx->uid, 0,
+		       sock_i_ino(&inet->sk),
+		       inet->sk.sk_refcnt.refs.counter, udp_sk,
+		       inet->sk.sk_drops.counter);
+
+	return 0;
+}

tools/testing/selftests/bpf/progs/bpf_iter_udp6.c

+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2020 Facebook */
+#include "bpf_iter.h"
+#include "bpf_tracing_net.h"
+#include <bpf/bpf_helpers.h>
+#include <bpf/bpf_tracing.h>
+#include <bpf/bpf_endian.h>
+
+char _license[] SEC("license") = "GPL";
+
+#define IPV6_SEQ_DGRAM_HEADER				\
+	"  sl  "					\
+	"local_address                         "	\
+	"remote_address                        "	\
+	"st tx_queue rx_queue tr tm->when retrnsmt"	\
+	"   uid  timeout inode ref pointer drops\n"
+
+static long sock_i_ino(const struct sock *sk)
+{
+	const struct socket *sk_socket = sk->sk_socket;
+	const struct inode *inode;
+	unsigned long ino;
+
+	if (!sk_socket)
+		return 0;
+
+	inode = &container_of(sk_socket, struct socket_alloc, socket)->vfs_inode;
+	bpf_probe_read(&ino, sizeof(ino), &inode->i_ino);
+	return ino;
+}
+
+SEC("iter/udp")
+int dump_udp6(struct bpf_iter__udp *ctx)
+{
+	struct seq_file *seq = ctx->meta->seq;
+	struct udp_sock *udp_sk = ctx->udp_sk;
+	const struct in6_addr *dest, *src;
+	struct udp6_sock *udp6_sk;
+	struct inet_sock *inet;
+	__u16 srcp, destp;
+	__u32 seq_num;
+	int rqueue;
+
+	if (udp_sk == (void *)0)
+		return 0;
+
+	seq_num = ctx->meta->seq_num;
+	if (seq_num == 0)
+		BPF_SEQ_PRINTF(seq, IPV6_SEQ_DGRAM_HEADER);
+
+	udp6_sk = bpf_skc_to_udp6_sock(udp_sk);
+	if (udp6_sk == (void *)0)
+		return 0;
+
+	inet = &udp_sk->inet;
+	srcp = bpf_ntohs(inet->inet_sport);
+	destp = bpf_ntohs(inet->inet_dport);
+	rqueue = inet->sk.sk_rmem_alloc.counter - udp_sk->forward_deficit;
+	dest  = &inet->sk.sk_v6_daddr;
+	src   = &inet->sk.sk_v6_rcv_saddr;
+
+	BPF_SEQ_PRINTF(seq, "%5d: %08X%08X%08X%08X:%04X %08X%08X%08X%08X:%04X ",
+		       ctx->bucket,
+		       src->s6_addr32[0], src->s6_addr32[1],
+		       src->s6_addr32[2], src->s6_addr32[3], srcp,
+		       dest->s6_addr32[0], dest->s6_addr32[1],
+		       dest->s6_addr32[2], dest->s6_addr32[3], destp);
+
+	BPF_SEQ_PRINTF(seq, "%02X %08X:%08X %02X:%08lX %08X %5u %8d %lu %d %pK %u\n",
+		       inet->sk.sk_state,
+		       inet->sk.sk_wmem_alloc.refs.counter - 1,
+		       rqueue,
+		       0, 0L, 0, ctx->uid, 0,
+		       sock_i_ino(&inet->sk),
+		       inet->sk.sk_refcnt.refs.counter, udp_sk,
+		       inet->sk.sk_drops.counter);
+
+	return 0;
+}