Re: [Patch bpf-next v2 8/9] sock_map: update sock type checks for UDP

On 3/3/21 10:02 AM, Cong Wang wrote:

On Tue, Mar 2, 2021 at 10:37 PM Yonghong Song [off-list ref] wrote:

quoted

On 3/1/21 6:37 PM, Cong Wang wrote:

quoted

From: Cong Wang <redacted>

Now UDP supports sockmap and redirection, we can safely update
the sock type checks for it accordingly.

Cc: John Fastabend <john.fastabend@gmail.com>
Cc: Daniel Borkmann <daniel@iogearbox.net>
Cc: Jakub Sitnicki <jakub@cloudflare.com>
Cc: Lorenz Bauer <redacted>
Signed-off-by: Cong Wang <redacted>
---
   net/core/sock_map.c | 5 ++++-
   1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/net/core/sock_map.c b/net/core/sock_map.c
index 13d2af5bb81c..f7eee4b7b994 100644
--- a/net/core/sock_map.c
+++ b/net/core/sock_map.c

@@ -549,7 +549,10 @@ static bool sk_is_udp(const struct sock *sk)

   static bool sock_map_redirect_allowed(const struct sock *sk)
   {
-     return sk_is_tcp(sk) && sk->sk_state != TCP_LISTEN;
+     if (sk_is_tcp(sk))
+             return sk->sk_state != TCP_LISTEN;
+     else
+             return sk->sk_state == TCP_ESTABLISHED;

Not a networking expert, a dump question. Here we tested
whether sk_is_tcp(sk) or not, if not we compare
sk->sk_state == TCP_ESTABLISHED, could this be
always false? Mostly I missed something, some comments
here will be good.

No, dgram sockets also use TCP_ESTABLISHED as a valid
state. I know its name looks confusing, but it is already widely
used in networking:

net/appletalk/ddp.c:    sk->sk_state = TCP_ESTABLISHED;
net/appletalk/ddp.c:            if (sk->sk_state != TCP_ESTABLISHED)
net/appletalk/ddp.c:            if (sk->sk_state != TCP_ESTABLISHED)
net/ax25/af_ax25.c:     sk->sk_state    = TCP_ESTABLISHED;
net/ax25/af_ax25.c:             case TCP_ESTABLISHED: /* connection
established */
net/ax25/af_ax25.c:     if (sk->sk_state == TCP_ESTABLISHED &&
sk->sk_type == SOCK_SEQPACKET) {
net/ax25/af_ax25.c:             sk->sk_state   = TCP_ESTABLISHED;
net/ax25/af_ax25.c:     if (sk->sk_state != TCP_ESTABLISHED && (flags
& O_NONBLOCK)) {
net/ax25/af_ax25.c:     if (sk->sk_state != TCP_ESTABLISHED) {
net/ax25/af_ax25.c:             if (sk->sk_state != TCP_ESTABLISHED) {
net/ax25/af_ax25.c:             if (sk->sk_state != TCP_ESTABLISHED) {
net/ax25/af_ax25.c:             if (sk->sk_state != TCP_ESTABLISHED) {
net/ax25/af_ax25.c:     if (sk->sk_type == SOCK_SEQPACKET &&
sk->sk_state != TCP_ESTABLISHED) {
net/ax25/ax25_ds_in.c:                  ax25->sk->sk_state = TCP_ESTABLISHED;
net/ax25/ax25_in.c:             make->sk_state = TCP_ESTABLISHED;
net/ax25/ax25_std_in.c:                         ax25->sk->sk_state =
TCP_ESTABLISHED;
net/caif/caif_socket.c: CAIF_CONNECTED          = TCP_ESTABLISHED,
net/ceph/messenger.c:   case TCP_ESTABLISHED:
net/ceph/messenger.c:           dout("%s TCP_ESTABLISHED\n", __func__);
net/core/datagram.c:        !(sk->sk_state == TCP_ESTABLISHED ||
sk->sk_state == TCP_LISTEN))
...

Hence, I believe it is okay to use it as it is, otherwise we would need
to comment on every use of it. ;)

That is okay. Thanks for explanation!

Thanks.