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 enabled by default. Can be disabled by setting both of
conf/{all,interface}/enhanced_dad to zero.
Signed-off-by: Erik Nordmark<nordm...@arista.com>
Signed-off-by: Bob Gilligan<gilli...@arista.com>"
---
v2: renamed sysctl and made it default to true, plus minor code review fixes
Index: net-next/Documentation/networking/ip-sysctl.txt
===================================================================
--- net-next.orig/Documentation/networking/ip-sysctl.txt
+++ net-next/Documentation/networking/ip-sysctl.txt
@@ -1729,6 +1729,15 @@ drop_unsolicited_na - BOOLEAN
By default this is turned off.
+enhanced_dad - 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 unless both of
+ conf/{all,interface}/enhanced_dad are set to FALSE.
+ Default: TRUE
+
icmp/*:
ratelimit - INTEGER
Limit the maximal rates for sending ICMPv6 packets.
Index: net-next/include/linux/ipv6.h
===================================================================
--- net-next.orig/include/linux/ipv6.h
+++ net-next/include/linux/ipv6.h
@@ -68,6 +68,7 @@ struct ipv6_devconf {
#ifdef CONFIG_IPV6_SEG6_HMAC
__s32 seg6_require_hmac;
#endif
+ __u32 enhanced_dad;
struct ctl_table_header *sysctl_header;
};
Index: net-next/include/net/if_inet6.h
===================================================================
--- net-next.orig/include/net/if_inet6.h
+++ net-next/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: net-next/include/net/ndisc.h
===================================================================
--- net-next.orig/include/net/ndisc.h
+++ net-next/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: net-next/include/uapi/linux/ipv6.h
===================================================================
--- net-next.orig/include/uapi/linux/ipv6.h
+++ net-next/include/uapi/linux/ipv6.h
@@ -181,6 +181,7 @@ enum {
DEVCONF_RTR_SOLICIT_MAX_INTERVAL,
DEVCONF_SEG6_ENABLED,
DEVCONF_SEG6_REQUIRE_HMAC,
+ DEVCONF_ENHANCED_DAD,
DEVCONF_MAX
};
Index: net-next/net/ipv6/addrconf.c
===================================================================
--- net-next.orig/net/ipv6/addrconf.c
+++ net-next/net/ipv6/addrconf.c
@@ -242,6 +242,7 @@ static struct ipv6_devconf ipv6_devconf
#ifdef CONFIG_IPV6_SEG6_HMAC
.seg6_require_hmac = 0,
#endif
+ .enhanced_dad = 1,
};
static struct ipv6_devconf ipv6_devconf_dflt __read_mostly = {
@@ -292,6 +293,7 @@ static struct ipv6_devconf ipv6_devconf_
#ifdef CONFIG_IPV6_SEG6_HMAC
.seg6_require_hmac = 0,
#endif
+ .enhanced_dad = 1,
};
/* Check if a valid qdisc is available */
@@ -3734,12 +3736,21 @@ 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 (idev->cnf.enhanced_dad ||
+ dev_net(idev->dev)->ipv6.devconf_all->enhanced_dad) {
+ do
+ get_random_bytes(&nonce, 6);
+ while (nonce == 0);
+ }
+ ifp->dad_nonce = nonce;
ifp->dad_probes = idev->cnf.dad_transmits;
addrconf_mod_dad_work(ifp, rand_num);
}
@@ -3915,7 +3926,8 @@ 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();
@@ -4956,6 +4968,7 @@ static inline void ipv6_store_devconf(st
#ifdef CONFIG_IPV6_SEG6_HMAC
array[DEVCONF_SEG6_REQUIRE_HMAC] = cnf->seg6_require_hmac;
#endif
+ array[DEVCONF_ENHANCED_DAD] = cnf->enhanced_dad;
}
static inline size_t inet6_ifla6_size(void)
@@ -6064,6 +6077,13 @@ static const struct ctl_table addrconf_s
},
#endif
{
+ .procname = "enhanced_dad",
+ .data = &ipv6_devconf.enhanced_dad,
+ .maxlen = sizeof(int),
+ .mode = 0644,
+ .proc_handler = proc_dointvec,
+ },
+ {
/* sentinel */
}
};
Index: net-next/net/ipv6/ndisc.c
===================================================================
--- net-next.orig/net/ipv6/ndisc.c
+++ net-next/net/ipv6/ndisc.c
@@ -233,6 +233,7 @@ 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,
@@ -568,7 +569,8 @@ 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;
@@ -588,6 +590,8 @@ 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)
@@ -605,6 +609,13 @@ 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);
}
@@ -693,12 +704,12 @@ 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);
}
}
@@ -742,6 +753,7 @@ static void ndisc_recv_ns(struct sk_buff
int dad = ipv6_addr_any(saddr);
bool inc;
int is_router = -1;
+ u64 nonce = 0;
if (skb->len < sizeof(struct nd_msg)) {
ND_PRINTK(2, warn, "NS: packet too short\n");
@@ -786,6 +798,8 @@ 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);
@@ -794,6 +808,17 @@ 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) {
+ u8 *np = (u8 *)&nonce;
+ /* Matching nonce if looped back */
+ ND_PRINTK(2, notice,
+ "%s: IPv6 DAD loopback for address
%pI6c nonce %02x:%02x:%02x:%02x:%02x:%02x ignored\n",
+ ifp->idev->dev->name,
+ &ifp->addr,
+ np[0], np[1], np[2], np[3],
+ np[4], np[5]);
+ goto out;
+ }
/*
* We are colliding with another node
* who is doing DAD
