Implemented RFC7527 Enhanced DAD.
IPv6 duplicate address detection can fail if there is some temporary
loopback of Ethernet frames. RFC7527 solves this by including a random
nonce in the NS messages used for DAD, and if an NS is received with the
same nonce it is assumed to be a looped back DAD probe and is ignored.
RFC7527 is disabled by default. Can be enabled by setting either one of
conf/{all,interface}/ipv6_rfc7527 to non-zero.
Signed-off-by: Erik Nordmark <nordm...@arista.com>
Index: linux-stable/Documentation/networking/ip-sysctl.txt
===================================================================
--- linux-stable.orig/Documentation/networking/ip-sysctl.txt
+++ linux-stable/Documentation/networking/ip-sysctl.txt
@@ -1713,6 +1713,15 @@ drop_unsolicited_na - BOOLEAN
By default this is turned off.
+ipv6_rfc7527 - BOOLEAN
+ Include a nonce option in the IPv6 neighbor solicitation messages
used for
+ duplicate address detection per RFC7527. A received DAD NS will
only signal
+ a duplicate address if the nonce is different. This avoids any false
+ detection of duplicates due to loopback of the NS messages that we
send.
+ The nonce option will be sent on an interface if either one of
+ conf/{all,interface}/ipv6_rfc7527 are TRUE.
+ Default: FALSE
+
icmp/*:
ratelimit - INTEGER
Limit the maximal rates for sending ICMPv6 packets.
Index: linux-stable/include/linux/ipv6.h
===================================================================
--- linux-stable.orig/include/linux/ipv6.h
+++ linux-stable/include/linux/ipv6.h
@@ -63,6 +63,7 @@ struct ipv6_devconf {
} stable_secret;
__s32 use_oif_addrs_only;
__s32 keep_addr_on_down;
+ __u32 ipv6_rfc7527;
struct ctl_table_header *sysctl_header;
};
Index: linux-stable/include/net/if_inet6.h
===================================================================
--- linux-stable.orig/include/net/if_inet6.h
+++ linux-stable/include/net/if_inet6.h
@@ -55,6 +55,7 @@ struct inet6_ifaddr {
__u8 stable_privacy_retry;
__u16 scope;
+ __u64 dad_nonce;
unsigned long cstamp; /* created timestamp */
unsigned long tstamp; /* updated timestamp */
Index: linux-stable/include/net/ndisc.h
===================================================================
--- linux-stable.orig/include/net/ndisc.h
+++ linux-stable/include/net/ndisc.h
@@ -31,6 +31,7 @@ enum {
ND_OPT_PREFIX_INFO = 3, /* RFC2461 */
ND_OPT_REDIRECT_HDR = 4, /* RFC2461 */
ND_OPT_MTU = 5, /* RFC2461 */
+ ND_OPT_NONCE = 14, /* RFC7527 */
__ND_OPT_ARRAY_MAX,
ND_OPT_ROUTE_INFO = 24, /* RFC4191 */
ND_OPT_RDNSS = 25, /* RFC5006 */
@@ -121,6 +122,7 @@ struct ndisc_options {
#define nd_opts_pi_end nd_opt_array[__ND_OPT_PREFIX_INFO_END]
#define nd_opts_rh nd_opt_array[ND_OPT_REDIRECT_HDR]
#define nd_opts_mtu nd_opt_array[ND_OPT_MTU]
+#define nd_opts_nonce nd_opt_array[ND_OPT_NONCE]
#define nd_802154_opts_src_lladdr
nd_802154_opt_array[ND_OPT_SOURCE_LL_ADDR]
#define nd_802154_opts_tgt_lladdr
nd_802154_opt_array[ND_OPT_TARGET_LL_ADDR]
@@ -398,7 +400,8 @@ void ndisc_cleanup(void);
int ndisc_rcv(struct sk_buff *skb);
void ndisc_send_ns(struct net_device *dev, const struct in6_addr *solicit,
- const struct in6_addr *daddr, const struct in6_addr *saddr);
+ const struct in6_addr *daddr, const struct in6_addr *saddr,
+ u64 nonce);
void ndisc_send_rs(struct net_device *dev,
const struct in6_addr *saddr, const struct in6_addr *daddr);
Index: linux-stable/include/uapi/linux/ipv6.h
===================================================================
--- linux-stable.orig/include/uapi/linux/ipv6.h
+++ linux-stable/include/uapi/linux/ipv6.h
@@ -177,6 +177,7 @@ enum {
DEVCONF_DROP_UNICAST_IN_L2_MULTICAST,
DEVCONF_DROP_UNSOLICITED_NA,
DEVCONF_KEEP_ADDR_ON_DOWN,
+ DEVCONF_IPV6_RFC7527,
DEVCONF_MAX
};
Index: linux-stable/net/ipv6/addrconf.c
===================================================================
--- linux-stable.orig/net/ipv6/addrconf.c
+++ linux-stable/net/ipv6/addrconf.c
@@ -217,6 +217,7 @@ static struct ipv6_devconf ipv6_devconf
.use_oif_addrs_only = 0,
.ignore_routes_with_linkdown = 0,
.keep_addr_on_down = 0,
+ .ipv6_rfc7527 = 0,
};
static struct ipv6_devconf ipv6_devconf_dflt __read_mostly = {
@@ -262,6 +263,7 @@ static struct ipv6_devconf ipv6_devconf_
.use_oif_addrs_only = 0,
.ignore_routes_with_linkdown = 0,
.keep_addr_on_down = 0,
+ .ipv6_rfc7527 = 0,
};
/* Check if a valid qdisc is available */
@@ -3722,12 +3724,18 @@ static void addrconf_dad_kick(struct ine
{
unsigned long rand_num;
struct inet6_dev *idev = ifp->idev;
+ u64 nonce;
if (ifp->flags & IFA_F_OPTIMISTIC)
rand_num = 0;
else
rand_num = prandom_u32() % (idev->cnf.rtr_solicit_delay ? : 1);
+ nonce = 0;
+ if (ifp->idev->cnf.ipv6_rfc7527 ||
+ dev_net((ifp->idev)->dev)->ipv6.devconf_all->ipv6_rfc7527)
+ get_random_bytes(&nonce, 6);
+ ifp->dad_nonce = nonce;
ifp->dad_probes = idev->cnf.dad_transmits;
addrconf_mod_dad_work(ifp, rand_num);
}
@@ -3903,7 +3911,8 @@ static void addrconf_dad_work(struct wor
/* send a neighbour solicitation for our addr */
addrconf_addr_solict_mult(&ifp->addr, &mcaddr);
- ndisc_send_ns(ifp->idev->dev, &ifp->addr, &mcaddr, &in6addr_any);
+ ndisc_send_ns(ifp->idev->dev, &ifp->addr, &mcaddr, &in6addr_any,
+ ifp->dad_nonce);
out:
in6_ifa_put(ifp);
rtnl_unlock();
@@ -4937,6 +4946,7 @@ static inline void ipv6_store_devconf(st
array[DEVCONF_DROP_UNICAST_IN_L2_MULTICAST] =
cnf->drop_unicast_in_l2_multicast;
array[DEVCONF_DROP_UNSOLICITED_NA] = cnf->drop_unsolicited_na;
array[DEVCONF_KEEP_ADDR_ON_DOWN] = cnf->keep_addr_on_down;
+ array[DEVCONF_IPV6_RFC7527] = cnf->ipv6_rfc7527;
}
static inline size_t inet6_ifla6_size(void)
@@ -6027,6 +6037,13 @@ static const struct ctl_table addrconf_s
},
{
+ .procname = "ipv6_rfc7527",
+ .data = &ipv6_devconf.ipv6_rfc7527,
+ .maxlen = sizeof(int),
+ .mode = 0644,
+ .proc_handler = proc_dointvec,
+ },
+ {
/* sentinel */
}
};
Index: linux-stable/net/ipv6/ndisc.c
===================================================================
--- linux-stable.orig/net/ipv6/ndisc.c
+++ linux-stable/net/ipv6/ndisc.c
@@ -234,6 +234,7 @@ struct ndisc_options *ndisc_parse_option
case ND_OPT_SOURCE_LL_ADDR:
case ND_OPT_TARGET_LL_ADDR:
case ND_OPT_MTU:
+ case ND_OPT_NONCE:
case ND_OPT_REDIRECT_HDR:
if (ndopts->nd_opt_array[nd_opt->nd_opt_type]) {
ND_PRINTK(2, warn,
@@ -571,7 +572,8 @@ static void ndisc_send_unsol_na(struct n
}
void ndisc_send_ns(struct net_device *dev, const struct in6_addr *solicit,
- const struct in6_addr *daddr, const struct in6_addr *saddr)
+ const struct in6_addr *daddr, const struct in6_addr *saddr,
+ u64 nonce)
{
struct sk_buff *skb;
struct in6_addr addr_buf;
@@ -591,6 +593,8 @@ void ndisc_send_ns(struct net_device *de
if (inc_opt)
optlen += ndisc_opt_addr_space(dev,
NDISC_NEIGHBOUR_SOLICITATION);
+ if (nonce != 0)
+ optlen += 8;
skb = ndisc_alloc_skb(dev, sizeof(*msg) + optlen);
if (!skb)
@@ -608,6 +612,13 @@ void ndisc_send_ns(struct net_device *de
ndisc_fill_addr_option(skb, ND_OPT_SOURCE_LL_ADDR,
dev->dev_addr,
NDISC_NEIGHBOUR_SOLICITATION);
+ if (nonce != 0) {
+ u8 *opt = skb_put(skb, 8);
+
+ opt[0] = ND_OPT_NONCE;
+ opt[1] = 8 >> 3;
+ memcpy(opt + 2, &nonce, 6);
+ }
ndisc_send_skb(skb, daddr, saddr);
}
@@ -696,12 +707,12 @@ static void ndisc_solicit(struct neighbo
"%s: trying to ucast probe in NUD_INVALID: %pI6\n",
__func__, target);
}
- ndisc_send_ns(dev, target, target, saddr);
+ ndisc_send_ns(dev, target, target, saddr, 0);
} else if ((probes -= NEIGH_VAR(neigh->parms, APP_PROBES)) < 0) {
neigh_app_ns(neigh);
} else {
addrconf_addr_solict_mult(target, &mcaddr);
- ndisc_send_ns(dev, target, &mcaddr, saddr);
+ ndisc_send_ns(dev, target, &mcaddr, saddr, 0);
}
}
@@ -745,6 +756,7 @@ static void ndisc_recv_ns(struct sk_buff
int dad = ipv6_addr_any(saddr);
bool inc;
int is_router = -1;
+ u64 nonce;
if (skb->len < sizeof(struct nd_msg)) {
ND_PRINTK(2, warn, "NS: packet too short\n");
@@ -789,6 +801,8 @@ static void ndisc_recv_ns(struct sk_buff
return;
}
}
+ if (ndopts.nd_opts_nonce)
+ memcpy(&nonce, (u8 *)(ndopts.nd_opts_nonce + 1), 6);
inc = ipv6_addr_is_multicast(daddr);
@@ -797,6 +811,16 @@ static void ndisc_recv_ns(struct sk_buff
have_ifp:
if (ifp->flags & (IFA_F_TENTATIVE|IFA_F_OPTIMISTIC)) {
if (dad) {
+ if (nonce != 0 && ifp->dad_nonce == nonce) {
+ /* Matching nonce if looped back */
+ if (net_ratelimit())
+ ND_PRINTK(2, notice,
+ "%s: IPv6 DAD loopback for address %pI6c
nonce %llu ignored\n",
+ ifp->idev->dev->name,
+ &ifp->addr,
+ nonce);
+ goto out;
+ }
/*
* We are colliding with another node
* who is doing DAD
