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

[Martin KaFai Lau <martin.lau@linux.dev>]

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 = {