tcp: ioctl type SIOCOUTQNSD returns amount of data not sent

In contrast to SIOCOUTQ which returns the amount of data sent
but not yet acknowledged plus data not yet sent this patch only
returns the data not sent.

For various methods of live streaming bitrate control it may
be helpful to know how much data are in the tcp outqueue are
not sent yet.

Signed-off-by: Mario Schuknecht <m.schuknecht@dresearch.de>
Signed-off-by: Steffen Sledz <sledz@dresearch.de>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 9 insertions, 0 deletions

diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index a17a5a72b98..b22d4501054 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -505,6 +505,15 @@ int tcp_ioctl(struct sock *sk, int cmd, unsigned long arg)
                 else
                         answ = tp->write_seq - tp->snd_una;
                 break;
+        case SIOCOUTQNSD:
+                if (sk->sk_state == TCP_LISTEN)
+                        return -EINVAL;
+
+                if ((1 << sk->sk_state) & (TCPF_SYN_SENT | TCPF_SYN_RECV))
+                        answ = 0;
+                else
+                        answ = tp->write_seq - tp->snd_nxt;
+                break;
         default:
                 return -ENOIOCTLCMD;
         }