From: Yonghong Song <yhs@fb.com>
Date: Tue, 23 Jun 2020 16:08:04 -0700
Subject: net: bpf: Add bpf_seq_afinfo in tcp_iter_state
Patch-mainline: v5.9-rc1
Git-commit: b08d4d3b6c0460306e8a0608413b201705200d33
References: bsc#1177028

A new field bpf_seq_afinfo is added to tcp_iter_state
to provide bpf tcp iterator afinfo. There are two
reasons on why we did this.

First, the current way to get afinfo from PDE_DATA
does not work for bpf iterator as its seq_file
inode does not conform to /proc/net/{tcp,tcp6}
inode structures. More specifically, anonymous
bpf iterator will use an anonymous inode which
is shared in the system and we cannot change inode
private data structure at all.

Second, bpf iterator for tcp/tcp6 wants to
traverse all tcp and tcp6 sockets in one pass
and bpf program can control whether they want
to skip one sk_family or not. Having a different
afinfo with family AF_UNSPEC make it easier
to understand in the code.

This patch does not change /proc/net/{tcp,tcp6} behavior
as the bpf_seq_afinfo will be NULL for these two proc files.

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/20200623230804.3987829-1-yhs@fb.com
Acked-by: Gary Lin <glin@suse.com>
---
 include/net/tcp.h   |    1 +
 net/ipv4/tcp_ipv4.c |   30 ++++++++++++++++++++++++------
 2 files changed, 25 insertions(+), 6 deletions(-)

--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -1929,6 +1929,7 @@ struct tcp_iter_state {
 	struct seq_net_private	p;
 	enum tcp_seq_states	state;
 	struct sock		*syn_wait_sk;
+	struct tcp_seq_afinfo	*bpf_seq_afinfo;
 	int			bucket, offset, sbucket, num;
 	loff_t			last_pos;
 };
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -2148,13 +2148,18 @@ EXPORT_SYMBOL(tcp_v4_destroy_sock);
  */
 static void *listening_get_next(struct seq_file *seq, void *cur)
 {
-	struct tcp_seq_afinfo *afinfo = PDE_DATA(file_inode(seq->file));
+	struct tcp_seq_afinfo *afinfo;
 	struct tcp_iter_state *st = seq->private;
 	struct net *net = seq_file_net(seq);
 	struct inet_listen_hashbucket *ilb;
 	struct hlist_nulls_node *node;
 	struct sock *sk = cur;
 
+	if (st->bpf_seq_afinfo)
+		afinfo = st->bpf_seq_afinfo;
+	else
+		afinfo = PDE_DATA(file_inode(seq->file));
+
 	if (!sk) {
 get_head:
 		ilb = &tcp_hashinfo.listening_hash[st->bucket];
@@ -2172,7 +2177,8 @@ get_sk:
 	sk_nulls_for_each_from(sk, node) {
 		if (!net_eq(sock_net(sk), net))
 			continue;
-		if (sk->sk_family == afinfo->family)
+		if (afinfo->family == AF_UNSPEC ||
+		    sk->sk_family == afinfo->family)
 			return sk;
 	}
 	spin_unlock(&ilb->lock);
@@ -2209,11 +2215,16 @@ static inline bool empty_bucket(const st
  */
 static void *established_get_first(struct seq_file *seq)
 {
-	struct tcp_seq_afinfo *afinfo = PDE_DATA(file_inode(seq->file));
+	struct tcp_seq_afinfo *afinfo;
 	struct tcp_iter_state *st = seq->private;
 	struct net *net = seq_file_net(seq);
 	void *rc = NULL;
 
+	if (st->bpf_seq_afinfo)
+		afinfo = st->bpf_seq_afinfo;
+	else
+		afinfo = PDE_DATA(file_inode(seq->file));
+
 	st->offset = 0;
 	for (; st->bucket <= tcp_hashinfo.ehash_mask; ++st->bucket) {
 		struct sock *sk;
@@ -2226,7 +2237,8 @@ static void *established_get_first(struc
 
 		spin_lock_bh(lock);
 		sk_nulls_for_each(sk, node, &tcp_hashinfo.ehash[st->bucket].chain) {
-			if (sk->sk_family != afinfo->family ||
+			if ((afinfo->family != AF_UNSPEC &&
+			     sk->sk_family != afinfo->family) ||
 			    !net_eq(sock_net(sk), net)) {
 				continue;
 			}
@@ -2241,19 +2253,25 @@ out:
 
 static void *established_get_next(struct seq_file *seq, void *cur)
 {
-	struct tcp_seq_afinfo *afinfo = PDE_DATA(file_inode(seq->file));
+	struct tcp_seq_afinfo *afinfo;
 	struct sock *sk = cur;
 	struct hlist_nulls_node *node;
 	struct tcp_iter_state *st = seq->private;
 	struct net *net = seq_file_net(seq);
 
+	if (st->bpf_seq_afinfo)
+		afinfo = st->bpf_seq_afinfo;
+	else
+		afinfo = PDE_DATA(file_inode(seq->file));
+
 	++st->num;
 	++st->offset;
 
 	sk = sk_nulls_next(sk);
 
 	sk_nulls_for_each_from(sk, node) {
-		if (sk->sk_family == afinfo->family &&
+		if ((afinfo->family == AF_UNSPEC ||
+		     sk->sk_family == afinfo->family) &&
 		    net_eq(sock_net(sk), net))
 			return sk;
 	}