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>

2 files changed, 12 insertions, 1 deletions

diff --git a/include/linux/sockios.h b/include/linux/sockios.h
index 241f179347d9..7997a506ad41 100644
--- a/include/linux/sockios.h
+++ b/include/linux/sockios.h
@@ -22,7 +22,7 @@
 
 /* Linux-specific socket ioctls */
 #define SIOCINQ         FIONREAD
-#define SIOCOUTQ        TIOCOUTQ
+#define SIOCOUTQ        TIOCOUTQ        /* output queue size (not sent + not acked) */
 
 /* Routing table calls. */
 #define SIOCADDRT       0x890B          /* add routing table entry      */
@@ -83,6 +83,8 @@
 
 #define SIOCWANDEV      0x894A          /* get/set netdev parameters    */
 
+#define SIOCOUTQNSD     0x894B          /* output queue size (not sent only) */
+
 /* ARP cache control calls. */
                     /*  0x8950 - 0x8952  * obsolete calls, don't re-use */
 #define SIOCDARP        0x8953          /* delete ARP table entry       */
diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index a17a5a72b98d..b22d45010545 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;
         }