net: dccp: Add SIOCOUTQ IOCTL support (send buffer fill)

This adds support for the SIOCOUTQ IOCTL to get the send buffer fill
of a DCCP socket, like UDP and TCP sockets already have.

Regarding the used data field: DCCP uses per packet sequence numbers,
not per byte, so sequence numbers can't be used like in TCP. sk_wmem_queued
is not used by DCCP and always 0, even in test on highly congested paths.
Therefore this uses sk_wmem_alloc like in UDP.

Signed-off-by: Richard Sailer <richard_siegfried@systemli.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/Documentation/networking/dccp.rst b/Documentation/networking/dccp.rst
index dde16be..91e5c33 100644 (file)
--- a/Documentation/networking/dccp.rst
+++ b/Documentation/networking/dccp.rst
@@ -192,6 +192,9 @@ FIONREAD
        Works as in udp(7): returns in the ``int`` argument pointer the size of
        the next pending datagram in bytes, or 0 when no datagram is pending.
 
+SIOCOUTQ
+       Returns the number of unsent data bytes in the socket send queue as ``int``
+       into the buffer specified by the argument pointer.
 
 Other tunables
 ==============

diff --git a/net/dccp/proto.c b/net/dccp/proto.c
index fd92d3f..9e45361 100644 (file)
--- a/net/dccp/proto.c
+++ b/net/dccp/proto.c
@@ -375,6 +375,15 @@ int dccp_ioctl(struct sock *sk, int cmd, unsigned long arg)
                goto out;
 
        switch (cmd) {
+       case SIOCOUTQ: {
+               int amount = sk_wmem_alloc_get(sk);
+               /* Using sk_wmem_alloc here because sk_wmem_queued is not used by DCCP and
+                * always 0, comparably to UDP.
+                */
+
+               rc = put_user(amount, (int __user *)arg);
+       }
+               break;
        case SIOCINQ: {
                struct sk_buff *skb;
                unsigned long amount = 0;