Re: [PATCH v5 bpf-next 3/7] udp: seq_file: Helper function to match socket attributes

Martin KaFai Lau
2023-03-31T20:09:47Z

On 3/30/23 8:17 AM, Aditi Ghag wrote:
> This is a preparatory commit to refactor code that matches socket
> attributes in iterators to a helper function, and use it in the
> proc fs iterator.
>
> Signed-off-by: Aditi Ghag <aditi.ghag@isovalent.com>
> ---
> net/ipv4/udp.c | 35 ++++++++++++++++++++++++++++-------
> 1 file changed, 28 insertions(+), 7 deletions(-)
>
> diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
> index c574c8c17ec9..cead4acb64c6 100644
> --- a/net/ipv4/udp.c
> +++ b/net/ipv4/udp.c
> @@ -2983,6 +2983,8 @@ EXPORT_SYMBOL(udp_prot);
> /* ------------------------------------------------------------------------ */
> #ifdef CONFIG_PROC_FS
>
> +static inline bool seq_sk_match(struct seq_file *seq, const struct sock *sk);
> +
> static struct udp_table *udp_get_table_afinfo(struct udp_seq_afinfo *afinfo,
> struct net *net)
> {
> @@ -3010,10 +3012,7 @@ static struct sock *udp_get_first(struct seq_file *seq, int start)
>
> spin_lock_bh(&hslot->lock);
> sk_for_each(sk, &hslot->head) {
> - if (!net_eq(sock_net(sk), net))
> - continue;
> - if (afinfo->family == AF_UNSPEC ||
> - sk->sk_family == afinfo->family)
> + if (seq_sk_match(seq, sk))
> goto found;
> }
> spin_unlock_bh(&hslot->lock);
> @@ -3034,9 +3033,7 @@ static struct sock *udp_get_next(struct seq_file *seq, struct sock *sk)
>
> do {
> sk = sk_next(sk);
> - } while (sk && (!net_eq(sock_net(sk), net) ||
> - (afinfo->family != AF_UNSPEC &&
> - sk->sk_family != afinfo->family)));
> + } while (sk && !seq_sk_match(seq, sk));
>
> if (!sk) {
> udptable = udp_get_table_afinfo(afinfo, net);
> @@ -3143,6 +3140,17 @@ struct bpf_iter__udp {
> int bucket __aligned(8);
> };
>
> +static unsigned short seq_file_family(const struct seq_file *seq);
> +
> +static inline bool seq_sk_match(struct seq_file *seq, const struct sock *sk)

This won't work under CONFIG_BPF_SYSCALL. The bot also complained.
It has to be under CONFIG_PROG_FS.

No need to use inline and leave it to compiler.

The earlier forward declaration is unnecessary. Define the function earlier instead.

> +{
> + unsigned short family = seq_file_family(seq);
> +
> + /* AF_UNSPEC is used as a match all */
> + return ((family == AF_UNSPEC || family == sk->sk_family) &&
> + net_eq(sock_net(sk), seq_file_net(seq)));
> +}
> +
> static int udp_prog_seq_show(struct bpf_prog *prog, struct bpf_iter_meta *meta,
> struct udp_sock *udp_sk, uid_t uid, int bucket)
> {
> @@ -3194,6 +3202,19 @@ static const struct seq_operations bpf_iter_udp_seq_ops = {
> .stop = bpf_iter_udp_seq_stop,
> .show = bpf_iter_udp_seq_show,
> };
> +
> +static unsigned short seq_file_family(const struct seq_file *seq)

The same here because seq_sk_match() uses seq_file_family().

> +{
> + const struct udp_seq_afinfo *afinfo;
> +
> + /* BPF iterator: bpf programs to filter sockets. */
> + if (seq->op == &bpf_iter_udp_seq_ops)

Note that bpf_iter_udp_seq_ops is only defined under CONFIG_BPF_SYSCALL though.
See how the seq_file_family() is handling it in tcp_ipv4.c.

> + return AF_UNSPEC;
> +
> + /* Proc fs iterator */
> + afinfo = pde_data(file_inode(seq->file));
> + return afinfo->family;
> +}
> #endif
>
> const struct seq_operations udp_seq_ops = {