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Message-ID: <20080422174152.GD6039@gerrit.erg.abdn.ac.uk>
Date: Tue, 22 Apr 2008 18:41:52 +0100
From: Gerrit Renker <gerrit@....abdn.ac.uk>
To: Tomasz Grobelny <tomasz@...belny.oswiecenia.net>
Cc: dccp@...r.kernel.org, netdev@...r.kernel.org
Subject: Re: [DCCP] [RFC] [Patchv2 1/1]: Queuing policies -- reworked
version of Tomasz's patch set
| If we iron this out we could finally return to the main subject of this
| thread. That is Patch v2 by me and Gerrit...
| --
Fully agree - we just need to decide whether or not to use skb->priority.
Below is as far as I got in integrating your patch last week, it shows
only the major changes. The following bits have been updated:
* skb->priority now cleared before passing the skb onto layer 3;
* order of statements in prio_push() reversed (first dropping worst
skb and then pushing the new skb - this is better when e.g.
tx_qlen=1);
* added general parsing routine for cmsg(3) socket control messages
and defined one for the SOL_DCCP socket level; thanks to advice
by Dave Miller
A new and updated version has been uploaded to
git://eden-feed.erg.abdn.ac.uk/dccp_exp
subtree `qpolicy'
The implementation needs some more testing.
I have uploaded matching userspace code to
http://www.erg.abdn.ac.uk/users/gerrit/dccp/packet_prio_tests.tar.gz
Will send an update next week and then we can discuss my edits, it
remains your patch. Simply too busy this week.
Gerrit
--- a/include/linux/dccp.h
+++ b/include/linux/dccp.h
@@ -195,6 +195,12 @@ enum dccp_feature_numbers {
DCCPF_MAX_CCID_SPECIFIC = 255,
};
+/* DCCP socket control message types for cmsg */
+enum dccp_cmsg_type {
+ DCCP_SCM_PRIORITY = 1,
+ DCCP_SCM_MAX
+};
+
/* DCCP priorities for outgoing/queued packets */
enum dccp_packet_dequeueing_policy {
DCCPQ_POLICY_SIMPLE,
--- a/net/dccp/proto.c
+++ b/net/dccp/proto.c
@@ -706,6 +706,32 @@ int compat_dccp_getsockopt(struct sock *
EXPORT_SYMBOL_GPL(compat_dccp_getsockopt);
#endif
+static int dccp_msghdr_parse(struct msghdr *msg, __u32 **priority)
+{
+ struct cmsghdr *cmsg = CMSG_FIRSTHDR(msg);
+
+ for (; cmsg != NULL; cmsg = CMSG_NXTHDR(msg, cmsg)) {
+
+ if (!CMSG_OK(msg, cmsg))
+ return -EINVAL;
+
+ /* Only look at DCCP-related socket control messages */
+ if (cmsg->cmsg_level != SOL_DCCP)
+ continue;
+
+ switch (cmsg->cmsg_type) {
+ case DCCP_SCM_PRIORITY:
+ if (cmsg->cmsg_len != CMSG_LEN(sizeof(__u32)))
+ return -EINVAL;
+ *priority = (__u32 *)CMSG_DATA(cmsg);
+ break;
+ default:
+ return -EINVAL;
+ }
+ }
+ return 0;
+}
+
int dccp_sendmsg(struct kiocb *iocb, struct sock *sk, struct msghdr *msg,
size_t len)
{
@@ -714,11 +740,15 @@ int dccp_sendmsg(struct kiocb *iocb, str
const int noblock = flags & MSG_DONTWAIT;
struct sk_buff *skb;
int rc, size;
+ __u32 *pprio = NULL;
long timeo;
if (len > dp->dccps_mss_cache)
return -EMSGSIZE;
+ if (dccp_msghdr_parse(msg, &pprio))
+ return -EINVAL;
+
lock_sock(sk);
if (dccp_qpolicy_full(sk)) {
@@ -749,7 +779,9 @@ int dccp_sendmsg(struct kiocb *iocb, str
if (rc != 0)
goto out_discard;
- dccp_qpolicy_push(sk, skb, msg);
+ skb->priority = pprio != NULL ? *pprio : 0;
+
+ dccp_qpolicy_push(sk, skb);
dccp_write_xmit(sk);
out_release:
release_sock(sk);
--- a/net/dccp/qpolicy.c
+++ b/net/dccp/qpolicy.c
@@ -97,13 +102,8 @@ static struct dccp_qpolicy_operations {
/*
* Externally visible interface
*/
-void dccp_qpolicy_push(struct sock *sk, struct sk_buff *skb, struct msghdr *msg)
+void dccp_qpolicy_push(struct sock *sk, struct sk_buff *skb)
{
- if (msg->msg_control == NULL || msg->msg_controllen != sizeof(__u32))
- skb->priority = 0; /* implies lowest-possible priority */
- else
- skb->priority = get_unaligned((__u32 *)msg->msg_control);
-
qpol_table[dccp_sk(sk)->dccps_qpolicy].push(sk, skb);
}
--- a/Documentation/networking/dccp.txt
+++ b/Documentation/networking/dccp.txt
@@ -51,7 +51,11 @@ during an established connection are not
defined: the "simple" policy (DCCPQ_POLICY_SIMPLE), which does nothing special,
and a priority-based variant (DCCPQ_POLICY_PRIO). The latter allows to pass an
u32 priority value as ancillary data to sendmsg(), where higher numbers indicate
-a higher packet priority (similar to SO_PRIORITY).
+a higher packet priority (similar to SO_PRIORITY). This ancillary data needs to
+be formatted using a cmsg(3) message header filled in as follows:
+ cmsg->cmsg_level = SOL_DCCP;
+ cmsg->cmsg_type = DCCP_SCM_PRIORITY;
+ cmsg->cmsg_len = CMSG_LEN(sizeof(uint32_t));
DCCP_SOCKOPT_QPOLICY_TXQLEN sets the maximum length of the output queue. A zero
value is always interpreted as unbounded queue length. If different from zero,
--- a/net/dccp/output.c
+++ b/net/dccp/output.c
@@ -257,6 +257,9 @@ static void dccp_xmit_packet(struct sock
DCCP_SKB_CB(skb)->dccpd_type = DCCP_PKT_DATA;
}
+ /* Clear priority value used by the qpolicy subsystem */
+ skb->priority = 0;
+
err = dccp_transmit_skb(sk, skb);
if (err)
dccp_pr_debug("transmit_skb() returned err=%d\n", err);
--
The University of Aberdeen is a charity registered in Scotland, No SC013683.
--
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