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carp: Set DSCP value CS7

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Update carp to set DSCP value CS7(Network Traffic) in the flowlabel field of
packets by default. Currently carp only sets TOS_LOWDELAY in IPv4 which was
deprecated in 1998. This also implements sysctl that can revert carp back to
it's old behavior if desired.

This will allow implementation of QOS on modern network devices to make sure
carp packets aren't dropped during interface contention.

Submitted by:	Nick Wolff <darkfiberiru AT gmail.com>
Reviewed by:	kp, mav (earlier version)
Differential Revision:	https://reviews.freebsd.org/D14536
This commit is contained in:
Kristof Provost 2018-07-01 08:37:07 +00:00
parent 4417ed2dbf
commit 0d3d234cd1
4 changed files with 44 additions and 2 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

8
share/man/man4/carp.4
View File

@ -26,7 +26,7 @@
.\"
.\" $FreeBSD$
.\"
.Dd May 7, 2018
.Dd July 1, 2018
.Dt CARP 4
.Os
.Sh NAME
@ -104,6 +104,12 @@ Allow virtual hosts to preempt each other.
When enabled, a vhid in a backup state would preempt a master that
is announcing itself with a lower advskew.
Disabled by default.
.It Va net.inet.carp.dscp
DSCP value in carp packet.
Valid Values are 0 to 63.
A value of 4 is equivalent to the old standard of TOS LOW_DELAY.
TOS values were deprecated and replaced by DSCP in 1998.
The default value is 56 (CS7/Network Control).
.It Va net.inet.carp.log
Determines what events relating to
.Nm

5
sys/netinet/ip.h
View File

@ -93,6 +93,11 @@ struct ip {
#define IPTOS_PREC_PRIORITY IPTOS_DSCP_CS1
#define IPTOS_PREC_ROUTINE IPTOS_DSCP_CS0
/*
* Offset of Diffserv decimal value to convert it to tos value .
*/
#define IPTOS_DSCP_OFFSET 2
/*
* Definitions for DiffServ Codepoints as per RFC2474 and RFC5865.
*/

1
sys/netinet/ip6.h
View File

@ -104,6 +104,7 @@ struct ip6_hdr {
#define IPV6_FLOWLABEL_MASK 0xffff0f00 /* flow label (20 bits) */
#endif /* LITTLE_ENDIAN */
#endif
#define IPV6_FLOWLABEL_LEN 20
#if 1
/* ECN bits proposed by Sally Floyd */
#define IP6TOS_CE 0x01 /* congestion experienced */

32
sys/netinet/ip_carp.c
View File

@ -190,6 +190,10 @@ static int proto_reg[] = {-1, -1};
static VNET_DEFINE(int, carp_allow) = 1;
#define V_carp_allow VNET(carp_allow)
/* Set DSCP in outgoing CARP packets. */
static VNET_DEFINE(int, carp_dscp) = 56;
#define V_carp_dscp VNET(carp_dscp)
/* Preempt slower nodes. */
static VNET_DEFINE(int, carp_preempt) = 0;
#define V_carp_preempt VNET(carp_preempt)
@ -211,12 +215,16 @@ static VNET_DEFINE(int, carp_ifdown_adj) = CARP_MAXSKEW;
#define V_carp_ifdown_adj VNET(carp_ifdown_adj)
static int carp_allow_sysctl(SYSCTL_HANDLER_ARGS);
static int carp_dscp_sysctl(SYSCTL_HANDLER_ARGS);
static int carp_demote_adj_sysctl(SYSCTL_HANDLER_ARGS);
SYSCTL_NODE(_net_inet, IPPROTO_CARP, carp, CTLFLAG_RW, 0, "CARP");
SYSCTL_PROC(_net_inet_carp, OID_AUTO, allow,
CTLFLAG_VNET | CTLTYPE_INT | CTLFLAG_RW, 0, 0, carp_allow_sysctl, "I",
"Accept incoming CARP packets");
SYSCTL_PROC(_net_inet_carp, OID_AUTO, dscp,
CTLFLAG_VNET | CTLTYPE_INT | CTLFLAG_RW, 0, 0, carp_dscp_sysctl, "I",
"DSCP value for carp packets");
SYSCTL_INT(_net_inet_carp, OID_AUTO, preempt, CTLFLAG_VNET | CTLFLAG_RW,
&VNET_NAME(carp_preempt), 0, "High-priority backup preemption mode");
SYSCTL_INT(_net_inet_carp, OID_AUTO, log, CTLFLAG_VNET | CTLFLAG_RW,
@ -933,7 +941,7 @@ carp_send_ad_locked(struct carp_softc *sc)
ip = mtod(m, struct ip *);
ip->ip_v = IPVERSION;
ip->ip_hl = sizeof(*ip) >> 2;
ip->ip_tos = IPTOS_LOWDELAY;
ip->ip_tos = V_carp_dscp << IPTOS_DSCP_OFFSET;
ip->ip_len = htons(len);
ip->ip_off = htons(IP_DF);
ip->ip_ttl = CARP_DFLTTL;
@ -983,6 +991,10 @@ carp_send_ad_locked(struct carp_softc *sc)
ip6 = mtod(m, struct ip6_hdr *);
bzero(ip6, sizeof(*ip6));
ip6->ip6_vfc |= IPV6_VERSION;
/* Traffic class isn't defined in ip6 struct instead
* it gets offset into flowid field */
ip6->ip6_flow |= htonl(V_carp_dscp << (IPV6_FLOWLABEL_LEN +
IPTOS_DSCP_OFFSET));
ip6->ip6_hlim = CARP_DFLTTL;
ip6->ip6_nxt = IPPROTO_CARP;
@ -2101,6 +2113,24 @@ carp_allow_sysctl(SYSCTL_HANDLER_ARGS)
return (0);
}
static int
carp_dscp_sysctl(SYSCTL_HANDLER_ARGS)
{
int new, error;
new = V_carp_dscp;
error = sysctl_handle_int(oidp, &new, 0, req);
if (error || !req->newptr)
return (error);
if (new < 0 || new > 63)
return (EINVAL);
V_carp_dscp = new;
return (0);
}
static int
carp_demote_adj_sysctl(SYSCTL_HANDLER_ARGS)
{