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

Aditi Ghag
2023-04-03T15:28:03Z

> On Mar 31, 2023, at 1:09 PM, Martin KaFai Lau <martin.lau@linux.dev> wrote:
>
> 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.

Yes, I got notifications from the kernel test bot, so I've already made the necessary changes.

>
>> +{
>> + 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.

Same as above.

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