On Wed, Jun 30, 2021 at 10:33 AM Jon Maloy <jma...@redhat.com> wrote:
>
>
> On 29/06/2021 17:41, Xin Long wrote:
> > On Tue, Jun 29, 2021 at 3:57 PM Jon Maloy <jma...@redhat.com> wrote:
> >>
> [...]
> > Yes, Jon, I mean the opposite.
> >
> > when MSG_EOR is set, we will go with what this patch does,
> > but to delete MSG_EOR if this is not the last part of the data,
> > and keep MSG_EOR if this is the last part of the data.
> >
> > when MSG_EOR is not set, the msg will be truncated as before.
>
> Yes, that would be a safe behavior. Is SCTP doing this?
No, SCTP doesn't need to, as it doesn't truncate msg since the beginning.
That's why no compatibility issue was caused.
>
> ///jon
>
> >
> >> In the first case, we don't solve any compatibility issue, if that is
> >> the purpose. The programmer still has to add code to get the current
> >> behavior.
> >>
> >> In the latter case we would be on the 100% safe side, although I have a
> >> real hard time to see that this could be a real issue. Why would anybody
> >> deliberately design an application for having messages truncated.
> >>
> >> ///jon
> >>
> >>
> >>>> to indicate we don't want the truncating msg.
> >>>>
> >>>> When the msg flag returns with no MSG_EOR, it means there's more data to
> >>>> read.
> >>>>
> >>>> Thanks.
> >>>>> - Erin
> >>>>>
> >>>>>> Signed-off-by: Xin Long <lucien....@gmail.com>
> >>>>>> ---
> >>>>>> net/tipc/socket.c | 30 +++++++++++++++++++++---------
> >>>>>> 1 file changed, 21 insertions(+), 9 deletions(-)
> >>>>>>
> >>>>>> diff --git a/net/tipc/socket.c b/net/tipc/socket.c
> >>>>>> index 34a97ea36cc8..504e59838b8b 100644
> >>>>>> --- a/net/tipc/socket.c
> >>>>>> +++ b/net/tipc/socket.c
> >>>>>> @@ -1880,6 +1880,7 @@ static int tipc_recvmsg(struct socket *sock,
> >>>>>> struct msghdr *m,
> >>>>>> bool connected = !tipc_sk_type_connectionless(sk);
> >>>>>> struct tipc_sock *tsk = tipc_sk(sk);
> >>>>>> int rc, err, hlen, dlen, copy;
> >>>>>> + struct tipc_skb_cb *skb_cb;
> >>>>>> struct sk_buff_head xmitq;
> >>>>>> struct tipc_msg *hdr;
> >>>>>> struct sk_buff *skb;
> >>>>>> @@ -1903,6 +1904,7 @@ static int tipc_recvmsg(struct socket *sock,
> >>>>>> struct msghdr *m,
> >>>>>> if (unlikely(rc))
> >>>>>> goto exit;
> >>>>>> skb = skb_peek(&sk->sk_receive_queue);
> >>>>>> + skb_cb = TIPC_SKB_CB(skb);
> >>>>>> hdr = buf_msg(skb);
> >>>>>> dlen = msg_data_sz(hdr);
> >>>>>> hlen = msg_hdr_sz(hdr);
> >>>>>> @@ -1922,18 +1924,27 @@ static int tipc_recvmsg(struct socket *sock,
> >>>>>> struct msghdr *m,
> >>>>>>
> >>>>>> /* Capture data if non-error msg, otherwise just set return
> >>>>>> value */
> >>>>>> if (likely(!err)) {
> >>>>>> - copy = min_t(int, dlen, buflen);
> >>>>>> - if (unlikely(copy != dlen))
> >>>>>> - m->msg_flags |= MSG_TRUNC;
> >>>>>> - rc = skb_copy_datagram_msg(skb, hlen, m, copy);
> >>>>>> + int offset = skb_cb->bytes_read;
> >>>>>> +
> >>>>>> + copy = min_t(int, dlen - offset, buflen);
> >>>>>> + rc = skb_copy_datagram_msg(skb, hlen + offset, m, copy);
> >>>>>> + if (unlikely(rc))
> >>>>>> + goto exit;
> >>>>>> + if (unlikely(offset + copy < dlen)) {
> >>>>>> + if (!(flags & MSG_PEEK))
> >>>>>> + skb_cb->bytes_read = offset + copy;
> >>>>>> + } else {
> >>>>>> + m->msg_flags |= MSG_EOR;
> >>>>>> + skb_cb->bytes_read = 0;
> >>>>>> + }
> >>>>>> } else {
> >>>>>> copy = 0;
> >>>>>> rc = 0;
> >>>>>> - if (err != TIPC_CONN_SHUTDOWN && connected &&
> >>>>>> !m->msg_control)
> >>>>>> + if (err != TIPC_CONN_SHUTDOWN && connected &&
> >>>>>> !m->msg_control) {
> >>>>>> rc = -ECONNRESET;
> >>>>>> + goto exit;
> >>>>>> + }
> >>>>>> }
> >>>>>> - if (unlikely(rc))
> >>>>>> - goto exit;
> >>>>>>
> >>>>>> /* Mark message as group event if applicable */
> >>>>>> if (unlikely(grp_evt)) {
> >>>>>> @@ -1956,9 +1967,10 @@ static int tipc_recvmsg(struct socket *sock,
> >>>>>> struct msghdr *m,
> >>>>>> tipc_node_distr_xmit(sock_net(sk), &xmitq);
> >>>>>> }
> >>>>>>
> >>>>>> - tsk_advance_rx_queue(sk);
> >>>>>> + if (!skb_cb->bytes_read)
> >>>>>> + tsk_advance_rx_queue(sk);
> >>>>>>
> >>>>>> - if (likely(!connected))
> >>>>>> + if (likely(!connected) || skb_cb->bytes_read)
> >>>>>> goto exit;
> >>>>>>
> >>>>>> /* Send connection flow control advertisement when applicable
> >>>>>> */
> >>>>>> --
> >>>>>> 2.27.0
> >>>>>>
> >>>>>>
> >>>>>>
> >>>>>> _______________________________________________
> >>>>>> tipc-discussion mailing list
> >>>>>> tipc-discussion@lists.sourceforge.net
> >>>>>> https://lists.sourceforge.net/lists/listinfo/tipc-discussion
> >>> _______________________________________________
> >>> tipc-discussion mailing list
> >>> tipc-discussion@lists.sourceforge.net
> >>> https://lists.sourceforge.net/lists/listinfo/tipc-discussion
> >>>
>
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