When data is peek'd off the receive queue we shouldn't considered it
copied from tcp_sock side. When we increment copied_seq this will confuse
tcp_data_ready() because copied_seq can be arbitrarily increased. From]
application side it results in poll() operations not waking up when
expected.
Notice tcp stack without BPF recvmsg programs also does not increment
copied_seq.
We broke this when we moved copied_seq into recvmsg to only update when
actual copy was happening. But, it wasn't working correctly either before
because the tcp_data_ready() tried to use the copied_seq value to see
if data was read by user yet. See fixes tags.
Fixes: e5c6de5fa0258 ("bpf, sockmap: Incorrectly handling copied_seq")
Fixes: 04919bed948dc ("tcp: Introduce tcp_read_skb()")
Reviewed-by: Jakub Sitnicki <jakub@xxxxxxxxxxxxxx>
Signed-off-by: John Fastabend <john.fastabend@xxxxxxxxx>
---
net/ipv4/tcp_bpf.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/net/ipv4/tcp_bpf.c b/net/ipv4/tcp_bpf.c
index 81f0dff69e0b..327268203001 100644
--- a/net/ipv4/tcp_bpf.c
+++ b/net/ipv4/tcp_bpf.c
@@ -222,6 +222,7 @@ static int tcp_bpf_recvmsg_parser(struct sock *sk,
int *addr_len)
{
struct tcp_sock *tcp = tcp_sk(sk);
+ int peek = flags & MSG_PEEK;
u32 seq = tcp->copied_seq;
struct sk_psock *psock;
int copied = 0;
@@ -311,7 +312,8 @@ static int tcp_bpf_recvmsg_parser(struct sock *sk,
copied = -EAGAIN;
}
out:
- WRITE_ONCE(tcp->copied_seq, seq);
+ if (!peek)
+ WRITE_ONCE(tcp->copied_seq, seq);
tcp_rcv_space_adjust(sk);
if (copied > 0)
__tcp_cleanup_rbuf(sk, copied);
--
2.33.0
