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

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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>
This commit is contained in:
Richard Sailer 2020-07-20 18:06:14 +02:00 committed by David S. Miller
parent 09a0d326b9
commit 749c08f820
2 changed files with 12 additions and 0 deletions
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3
Documentation/networking/dccp.rst
View file

@ -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
==============

9
net/dccp/proto.c
View file

@ -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;