udp: seq_file: Helper function to match socket attributes

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>
Link: https://lore.kernel.org/r/20230519225157.760788-3-aditi.ghag@isovalent.com
Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>

Author: aditighag

net/ipv4/udp.c

@@ -2988,6 +2988,16 @@ EXPORT_SYMBOL(udp_prot);
 /* ------------------------------------------------------------------------ */
 #ifdef CONFIG_PROC_FS
 
+static unsigned short seq_file_family(const struct seq_file *seq);
+static bool seq_sk_match(struct seq_file *seq, const struct sock *sk)
+{
+	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 struct udp_table *udp_get_table_afinfo(struct udp_seq_afinfo *afinfo,
 					      struct net *net)
 {
@@ -3018,10 +3028,7 @@ 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);
@@ -3045,9 +3052,7 @@ 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);
@@ -3210,6 +3215,21 @@ static const struct seq_operations bpf_iter_udp_seq_ops = {
 };
 #endif
 
+static unsigned short seq_file_family(const struct seq_file *seq)
+{
+	const struct udp_seq_afinfo *afinfo;
+
+#ifdef CONFIG_BPF_SYSCALL
+	/* BPF iterator: bpf programs to filter sockets. */
+	if (seq->op == &bpf_iter_udp_seq_ops)
+		return AF_UNSPEC;
+#endif
+
+	/* Proc fs iterator */
+	afinfo = pde_data(file_inode(seq->file));
+	return afinfo->family;
+}
+
 const struct seq_operations udp_seq_ops = {
 	.start		= udp_seq_start,
 	.next		= udp_seq_next,