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dccp: Policy-based packet dequeueing infrastructure

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This patch adds a generic infrastructure for policy-based dequeueing of
TX packets and provides two policies:
 * a simple FIFO policy (which is the default) and
 * a priority based policy (set via socket options).
Both policies honour the tx_qlen sysctl for the maximum size of the write
queue (can be overridden via socket options).

The priority policy uses skb->priority internally to assign an u32 priority
identifier, using the same ranking as SO_PRIORITY. The skb->priority field
is set to 0 when the packet leaves DCCP. The priority is supplied as ancillary
data using cmsg(3), the patch also provides the requisite parsing routines.

Signed-off-by: Tomasz Grobelny <tomasz@grobelny.oswiecenia.net>
Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk>
This commit is contained in:
Tomasz Grobelny 2010-12-04 13:38:01 +01:00 committed by Gerrit Renker
parent cfa969e385
commit 871a2c16c2
7 changed files with 248 additions and 9 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

20
Documentation/networking/dccp.txt
View File

@ -47,6 +47,26 @@ http://linux-net.osdl.org/index.php/DCCP_Testing#Experimental_DCCP_source_tree
Socket options
==============
DCCP_SOCKOPT_QPOLICY_ID sets the dequeuing policy for outgoing packets. It takes
a policy ID as argument and can only be set before the connection (i.e. changes
during an established connection are not supported). Currently, two policies are
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). 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)); /* or CMSG_LEN(4) */
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,
the interpretation of this parameter depends on the current dequeuing policy
(see above): the "simple" policy will enforce a fixed queue size by returning
EAGAIN, whereas the "prio" policy enforces a fixed queue length by dropping the
lowest-priority packet first. The default value for this parameter is
initialised from /proc/sys/net/dccp/default/tx_qlen.
DCCP_SOCKOPT_SERVICE sets the service. The specification mandates use of
service codes (RFC 4340, sec. 8.1.2); if this socket option is not set,
the socket will fall back to 0 (which means that no meaningful service code

21
include/linux/dccp.h
View File

@ -197,6 +197,21 @@ 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_QPOLICY_MAX = 0xFFFF,
/* ^-- Up to here reserved exclusively for qpolicy parameters */
DCCP_SCM_MAX
};
/* DCCP priorities for outgoing/queued packets */
enum dccp_packet_dequeueing_policy {
DCCPQ_POLICY_SIMPLE,
DCCPQ_POLICY_PRIO,
DCCPQ_POLICY_MAX
};
/* DCCP socket options */
#define DCCP_SOCKOPT_PACKET_SIZE 1 /* XXX deprecated, without effect */
#define DCCP_SOCKOPT_SERVICE 2
@ -210,6 +225,8 @@ enum dccp_feature_numbers {
#define DCCP_SOCKOPT_CCID 13
#define DCCP_SOCKOPT_TX_CCID 14
#define DCCP_SOCKOPT_RX_CCID 15
#define DCCP_SOCKOPT_QPOLICY_ID 16
#define DCCP_SOCKOPT_QPOLICY_TXQLEN 17
#define DCCP_SOCKOPT_CCID_RX_INFO 128
#define DCCP_SOCKOPT_CCID_TX_INFO 192
@ -458,6 +475,8 @@ struct dccp_ackvec;
* @dccps_hc_rx_ccid - CCID used for the receiver (or receiving half-connection)
* @dccps_hc_tx_ccid - CCID used for the sender (or sending half-connection)
* @dccps_options_received - parsed set of retrieved options
* @dccps_qpolicy - TX dequeueing policy, one of %dccp_packet_dequeueing_policy
* @dccps_tx_qlen - maximum length of the TX queue
* @dccps_role - role of this sock, one of %dccp_role
* @dccps_hc_rx_insert_options - receiver wants to add options when acking
* @dccps_hc_tx_insert_options - sender wants to add options when sending
@ -500,6 +519,8 @@ struct dccp_sock {
struct ccid *dccps_hc_rx_ccid;
struct ccid *dccps_hc_tx_ccid;
struct dccp_options_received dccps_options_received;
__u8 dccps_qpolicy;
__u32 dccps_tx_qlen;
enum dccp_role dccps_role:2;
__u8 dccps_hc_rx_insert_options:1;
__u8 dccps_hc_tx_insert_options:1;

4
net/dccp/Makefile
View File

@ -1,7 +1,7 @@
obj-$(CONFIG_IP_DCCP) += dccp.o dccp_ipv4.o
dccp-y := ccid.o feat.o input.o minisocks.o options.o output.o proto.o timer.o
dccp-y := ccid.o feat.o input.o minisocks.o options.o output.o proto.o timer.o \
qpolicy.o
#
# CCID algorithms to be used by dccp.ko
#

12
net/dccp/dccp.h
View File

@ -243,6 +243,18 @@ extern void dccp_reqsk_send_ack(struct sock *sk, struct sk_buff *skb,
extern void dccp_send_sync(struct sock *sk, const u64 seq,
const enum dccp_pkt_type pkt_type);
/*
* TX Packet Dequeueing Interface
*/
extern void dccp_qpolicy_push(struct sock *sk, struct sk_buff *skb);
extern bool dccp_qpolicy_full(struct sock *sk);
extern void dccp_qpolicy_drop(struct sock *sk, struct sk_buff *skb);
extern struct sk_buff *dccp_qpolicy_top(struct sock *sk);
extern struct sk_buff *dccp_qpolicy_pop(struct sock *sk);
/*
* TX Packet Output and TX Timers
*/
extern void dccp_write_xmit(struct sock *sk);
extern void dccp_write_space(struct sock *sk);
extern void dccp_flush_write_queue(struct sock *sk, long *time_budget);

7
net/dccp/output.c
View File

@ -242,7 +242,7 @@ static void dccp_xmit_packet(struct sock *sk)
{
int err, len;
struct dccp_sock *dp = dccp_sk(sk);
struct sk_buff *skb = skb_dequeue(&sk->sk_write_queue);
struct sk_buff *skb = dccp_qpolicy_pop(sk);
if (unlikely(skb == NULL))
return;
@ -345,7 +345,7 @@ void dccp_write_xmit(struct sock *sk)
struct dccp_sock *dp = dccp_sk(sk);
struct sk_buff *skb;
while ((skb = skb_peek(&sk->sk_write_queue))) {
while ((skb = dccp_qpolicy_top(sk))) {
int rc = ccid_hc_tx_send_packet(dp->dccps_hc_tx_ccid, sk, skb);
switch (ccid_packet_dequeue_eval(rc)) {
@ -359,8 +359,7 @@ void dccp_write_xmit(struct sock *sk)
dccp_xmit_packet(sk);
break;
case CCID_PACKET_ERR:
skb_dequeue(&sk->sk_write_queue);
kfree_skb(skb);
dccp_qpolicy_drop(sk, skb);
dccp_pr_debug("packet discarded due to err=%d\n", rc);
}
}

67
net/dccp/proto.c
View File

@ -185,6 +185,7 @@ int dccp_init_sock(struct sock *sk, const __u8 ctl_sock_initialized)
dp->dccps_role = DCCP_ROLE_UNDEFINED;
dp->dccps_service = DCCP_SERVICE_CODE_IS_ABSENT;
dp->dccps_l_ack_ratio = dp->dccps_r_ack_ratio = 1;
dp->dccps_tx_qlen = sysctl_dccp_tx_qlen;
dccp_init_xmit_timers(sk);
@ -532,6 +533,20 @@ static int do_dccp_setsockopt(struct sock *sk, int level, int optname,
case DCCP_SOCKOPT_RECV_CSCOV:
err = dccp_setsockopt_cscov(sk, val, true);
break;
case DCCP_SOCKOPT_QPOLICY_ID:
if (sk->sk_state != DCCP_CLOSED)
err = -EISCONN;
else if (val < 0 || val >= DCCPQ_POLICY_MAX)
err = -EINVAL;
else
dp->dccps_qpolicy = val;
break;
case DCCP_SOCKOPT_QPOLICY_TXQLEN:
if (val < 0)
err = -EINVAL;
else
dp->dccps_tx_qlen = val;
break;
default:
err = -ENOPROTOOPT;
break;
@ -639,6 +654,12 @@ static int do_dccp_getsockopt(struct sock *sk, int level, int optname,
case DCCP_SOCKOPT_RECV_CSCOV:
val = dp->dccps_pcrlen;
break;
case DCCP_SOCKOPT_QPOLICY_ID:
val = dp->dccps_qpolicy;
break;
case DCCP_SOCKOPT_QPOLICY_TXQLEN:
val = dp->dccps_tx_qlen;
break;
case 128 ... 191:
return ccid_hc_rx_getsockopt(dp->dccps_hc_rx_ccid, sk, optname,
len, (u32 __user *)optval, optlen);
@ -681,6 +702,43 @@ int compat_dccp_getsockopt(struct sock *sk, int level, int optname,
EXPORT_SYMBOL_GPL(compat_dccp_getsockopt);
#endif
static int dccp_msghdr_parse(struct msghdr *msg, struct sk_buff *skb)
{
struct cmsghdr *cmsg = CMSG_FIRSTHDR(msg);
/*
* Assign an (opaque) qpolicy priority value to skb->priority.
*
* We are overloading this skb field for use with the qpolicy subystem.
* The skb->priority is normally used for the SO_PRIORITY option, which
* is initialised from sk_priority. Since the assignment of sk_priority
* to skb->priority happens later (on layer 3), we overload this field
* for use with queueing priorities as long as the skb is on layer 4.
* The default priority value (if nothing is set) is 0.
*/
skb->priority = 0;
for (; cmsg != NULL; cmsg = CMSG_NXTHDR(msg, cmsg)) {
if (!CMSG_OK(msg, cmsg))
return -EINVAL;
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;
skb->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)
{
@ -696,8 +754,7 @@ int dccp_sendmsg(struct kiocb *iocb, struct sock *sk, struct msghdr *msg,
lock_sock(sk);
if (sysctl_dccp_tx_qlen &&
(sk->sk_write_queue.qlen >= sysctl_dccp_tx_qlen)) {
if (dccp_qpolicy_full(sk)) {
rc = -EAGAIN;
goto out_release;
}
@ -725,7 +782,11 @@ int dccp_sendmsg(struct kiocb *iocb, struct sock *sk, struct msghdr *msg,
if (rc != 0)
goto out_discard;
skb_queue_tail(&sk->sk_write_queue, skb);
rc = dccp_msghdr_parse(msg, skb);
if (rc != 0)
goto out_discard;
dccp_qpolicy_push(sk, skb);
/*
* The xmit_timer is set if the TX CCID is rate-based and will expire
* when congestion control permits to release further packets into the

126
net/dccp/qpolicy.c Normal file
View File

@ -0,0 +1,126 @@
/*
* net/dccp/qpolicy.c
*
* Policy-based packet dequeueing interface for DCCP.
*
* Copyright (c) 2008 Tomasz Grobelny <tomasz@grobelny.oswiecenia.net>
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License v2
* as published by the Free Software Foundation.
*/
#include "dccp.h"
/*
* Simple Dequeueing Policy:
* If tx_qlen is different from 0, enqueue up to tx_qlen elements.
*/
static void qpolicy_simple_push(struct sock *sk, struct sk_buff *skb)
{
skb_queue_tail(&sk->sk_write_queue, skb);
}
static bool qpolicy_simple_full(struct sock *sk)
{
return dccp_sk(sk)->dccps_tx_qlen &&
sk->sk_write_queue.qlen >= dccp_sk(sk)->dccps_tx_qlen;
}
static struct sk_buff *qpolicy_simple_top(struct sock *sk)
{
return skb_peek(&sk->sk_write_queue);
}
/*
* Priority-based Dequeueing Policy:
* If tx_qlen is different from 0 and the queue has reached its upper bound
* of tx_qlen elements, replace older packets lowest-priority-first.
*/
static struct sk_buff *qpolicy_prio_best_skb(struct sock *sk)
{
struct sk_buff *skb, *best = NULL;
skb_queue_walk(&sk->sk_write_queue, skb)
if (best == NULL || skb->priority > best->priority)
best = skb;
return best;
}
static struct sk_buff *qpolicy_prio_worst_skb(struct sock *sk)
{
struct sk_buff *skb, *worst = NULL;
skb_queue_walk(&sk->sk_write_queue, skb)
if (worst == NULL || skb->priority < worst->priority)
worst = skb;
return worst;
}
static bool qpolicy_prio_full(struct sock *sk)
{
if (qpolicy_simple_full(sk))
dccp_qpolicy_drop(sk, qpolicy_prio_worst_skb(sk));
return false;
}
/**
* struct dccp_qpolicy_operations - TX Packet Dequeueing Interface
* @push: add a new @skb to the write queue
* @full: indicates that no more packets will be admitted
* @top: peeks at whatever the queueing policy defines as its `top'
*/
static struct dccp_qpolicy_operations {
void (*push) (struct sock *sk, struct sk_buff *skb);
bool (*full) (struct sock *sk);
struct sk_buff* (*top) (struct sock *sk);
} qpol_table[DCCPQ_POLICY_MAX] = {
[DCCPQ_POLICY_SIMPLE] = {
.push = qpolicy_simple_push,
.full = qpolicy_simple_full,
.top = qpolicy_simple_top,
},
[DCCPQ_POLICY_PRIO] = {
.push = qpolicy_simple_push,
.full = qpolicy_prio_full,
.top = qpolicy_prio_best_skb,
},
};
/*
* Externally visible interface
*/
void dccp_qpolicy_push(struct sock *sk, struct sk_buff *skb)
{
qpol_table[dccp_sk(sk)->dccps_qpolicy].push(sk, skb);
}
bool dccp_qpolicy_full(struct sock *sk)
{
return qpol_table[dccp_sk(sk)->dccps_qpolicy].full(sk);
}
void dccp_qpolicy_drop(struct sock *sk, struct sk_buff *skb)
{
if (skb != NULL) {
skb_unlink(skb, &sk->sk_write_queue);
kfree_skb(skb);
}
}
struct sk_buff *dccp_qpolicy_top(struct sock *sk)
{
return qpol_table[dccp_sk(sk)->dccps_qpolicy].top(sk);
}
struct sk_buff *dccp_qpolicy_pop(struct sock *sk)
{
struct sk_buff *skb = dccp_qpolicy_top(sk);
if (skb != NULL) {
/* Clear any skb fields that we used internally */
skb->priority = 0;
skb_unlink(skb, &sk->sk_write_queue);
}
return skb;
}