net: bpf: Add bpf_seq_afinfo in udp_iter_state

Similar to tcp_iter_state, a new field bpf_seq_afinfo is
added to udp_iter_state to provide bpf udp iterator
afinfo.

This does not change /proc/net/{udp, udp6} behavior. But
it enables bpf iterator to avoid get afinfo from PDE_DATA
and iterate through all udp and udp6 sockets in one pass.
Signed-off-by: Yonghong Song <yhs@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Martin KaFai Lau <kafai@fb.com>
Link: https://lore.kernel.org/bpf/20200623230812.3988347-1-yhs@fb.com

include/net/udp.h

@@ -440,6 +440,7 @@ struct udp_seq_afinfo {
 struct udp_iter_state {
 	struct seq_net_private  p;
 	int			bucket;
+	struct udp_seq_afinfo	*bpf_seq_afinfo;
 };
 
 void *udp_seq_start(struct seq_file *seq, loff_t *pos);

net/ipv4/udp.c

@@ -2826,10 +2826,15 @@ EXPORT_SYMBOL(udp_prot);
 static struct sock *udp_get_first(struct seq_file *seq, int start)
 {
 	struct sock *sk;
-	struct udp_seq_afinfo *afinfo = PDE_DATA(file_inode(seq->file));
+	struct udp_seq_afinfo *afinfo;
 	struct udp_iter_state *state = seq->private;
 	struct net *net = seq_file_net(seq);
 
+	if (state->bpf_seq_afinfo)
+		afinfo = state->bpf_seq_afinfo;
+	else
+		afinfo = PDE_DATA(file_inode(seq->file));
+
 	for (state->bucket = start; state->bucket <= afinfo->udp_table->mask;
 	     ++state->bucket) {
 		struct udp_hslot *hslot = &afinfo->udp_table->hash[state->bucket];
@@ -2841,7 +2846,8 @@ static struct sock *udp_get_first(struct seq_file *seq, int start)
 		sk_for_each(sk, &hslot->head) {
 			if (!net_eq(sock_net(sk), net))
 				continue;
-			if (sk->sk_family == afinfo->family)
+			if (afinfo->family == AF_UNSPEC ||
+			    sk->sk_family == afinfo->family)
 				goto found;
 		}
 		spin_unlock_bh(&hslot->lock);
@@ -2853,13 +2859,20 @@ static struct sock *udp_get_first(struct seq_file *seq, int start)
 
 static struct sock *udp_get_next(struct seq_file *seq, struct sock *sk)
 {
-	struct udp_seq_afinfo *afinfo = PDE_DATA(file_inode(seq->file));
+	struct udp_seq_afinfo *afinfo;
 	struct udp_iter_state *state = seq->private;
 	struct net *net = seq_file_net(seq);
 
+	if (state->bpf_seq_afinfo)
+		afinfo = state->bpf_seq_afinfo;
+	else
+		afinfo = PDE_DATA(file_inode(seq->file));
+
 	do {
 		sk = sk_next(sk);
-	} while (sk && (!net_eq(sock_net(sk), net) || sk->sk_family != afinfo->family));
+	} while (sk && (!net_eq(sock_net(sk), net) ||
+			(afinfo->family != AF_UNSPEC &&
+			 sk->sk_family != afinfo->family)));
 
 	if (!sk) {
 		if (state->bucket <= afinfo->udp_table->mask)
@@ -2904,9 +2917,14 @@ EXPORT_SYMBOL(udp_seq_next);
 
 void udp_seq_stop(struct seq_file *seq, void *v)
 {
-	struct udp_seq_afinfo *afinfo = PDE_DATA(file_inode(seq->file));
+	struct udp_seq_afinfo *afinfo;
 	struct udp_iter_state *state = seq->private;
 
+	if (state->bpf_seq_afinfo)
+		afinfo = state->bpf_seq_afinfo;
+	else
+		afinfo = PDE_DATA(file_inode(seq->file));
+
 	if (state->bucket <= afinfo->udp_table->mask)
 		spin_unlock_bh(&afinfo->udp_table->hash[state->bucket].lock);
 }