* [PATCH net-next 0/2] ipv6: report why a route was deleted in RTM_DELROUTE
@ 2026-07-17 22:23 Yuyang Huang
2026-07-17 22:23 ` [PATCH net-next 1/2] " Yuyang Huang
2026-07-17 22:23 ` [PATCH net-next 2/2] selftests: net: verify RTA_DEL_REASON on route deletion Yuyang Huang
0 siblings, 2 replies; 3+ messages in thread
From: Yuyang Huang @ 2026-07-17 22:23 UTC (permalink / raw)
To: Yuyang Huang
Cc: David S. Miller, Bobby Eshleman, Chris J Arges, Daniel Zahka,
David Ahern, David Wei, Dimitri Daskalakis, Donald Hunter,
Eric Dumazet, Gal Pressman, Ido Schimmel, Jakub Kicinski,
Paolo Abeni, Shuah Khan, Simon Horman, Stanislav Fomichev,
Willem de Bruijn, linux-kernel, linux-kselftest, netdev
When the kernel deletes an IPv6 route on its own, the RTM_DELROUTE
notification does not say why. User space cannot tell a route that
expired from one the router explicitly withdrew, yet the two call for
different reactions: an expired RA route means the router failed to
refresh it in time, which points at a misconfigured or unreliable
router and may warrant action such as disabling IPv6 on that network,
while a zero-lifetime withdrawal is normal, RFC-compliant operation.
Patch 1 adds RTA_DEL_REASON (u8) to RTM_DELROUTE notifications and
records the cause in the kernel-initiated IPv6 deletion paths:
RTA_DEL_REASON_EXPIRED for routes garbage collected after their
RTF_EXPIRES lifetime ran out, and RTA_DEL_REASON_RA_WITHDRAWN for
default routes, prefix routes and RFC 4191 route information routes
withdrawn by Router Advertisements. The rt-route Netlink spec is
extended with the attribute, the route notifications and their
multicast groups.
Only kernel-initiated deletions that user space cannot otherwise
explain are attributed. User-requested deletions are self-explanatory
to the requester, so they carry no reason; the UAPI documents that
absence and RTA_DEL_REASON_UNSPEC must be treated identically, which
keeps the door open for attributing more paths (nexthop removal
cascades, device removal) later.
Patch 2 adds selftests covering all three producer paths: a GC-expired
route, and a default route + PIO prefix route + RIO route advertised
and then withdrawn by hand-crafted RAs over a raw ICMPv6 socket (no
external RA tool needed), plus a check that user-requested deletions
carry no attribute. The notifications are decoded with YNL, which also
exercises the rt-route spec additions.
Yuyang Huang (2):
ipv6: report why a route was deleted in RTM_DELROUTE
selftests: net: verify RTA_DEL_REASON on route deletion
Documentation/netlink/specs/rt-route.yaml | 33 ++++
include/net/ip6_fib.h | 4 +-
include/net/ip6_route.h | 2 +
include/uapi/linux/rtnetlink.h | 17 ++
net/ipv6/addrconf.c | 3 +-
net/ipv6/ip6_fib.c | 19 +-
net/ipv6/ndisc.c | 7 +-
net/ipv6/route.c | 66 ++++---
.../testing/selftests/net/lib/py/__init__.py | 4 +-
tools/testing/selftests/net/lib/py/ynl.py | 7 +-
tools/testing/selftests/net/rtnetlink.py | 181 +++++++++++++++++-
11 files changed, 303 insertions(+), 40 deletions(-)
--
2.43.0
^ permalink raw reply [flat|nested] 3+ messages in thread
* [PATCH net-next 1/2] ipv6: report why a route was deleted in RTM_DELROUTE
2026-07-17 22:23 [PATCH net-next 0/2] ipv6: report why a route was deleted in RTM_DELROUTE Yuyang Huang
@ 2026-07-17 22:23 ` Yuyang Huang
2026-07-17 22:23 ` [PATCH net-next 2/2] selftests: net: verify RTA_DEL_REASON on route deletion Yuyang Huang
1 sibling, 0 replies; 3+ messages in thread
From: Yuyang Huang @ 2026-07-17 22:23 UTC (permalink / raw)
To: Yuyang Huang
Cc: David S. Miller, Bobby Eshleman, Chris J Arges, Daniel Zahka,
David Ahern, David Wei, Dimitri Daskalakis, Donald Hunter,
Eric Dumazet, Gal Pressman, Ido Schimmel, Jakub Kicinski,
Paolo Abeni, Shuah Khan, Simon Horman, Stanislav Fomichev,
Willem de Bruijn, linux-kernel, linux-kselftest, netdev
Add RTA_DEL_REASON (u8) to RTM_DELROUTE notifications to report the
cause of kernel-initiated IPv6 route deletions, so user space can tell
routes that expired from routes explicitly withdrawn by Router
Advertisements.
The two causes call for different treatment in user space. An expired
RA route means the router failed to refresh it before its lifetime ran
out, which points at a misconfigured or unreliable router; user space
may want to react, for example by disabling IPv6 on that network
entirely. An RA withdrawal (zero lifetime) is valid, RFC-compliant
operation and needs no such recovery. Today both surface as an
identical RTM_DELROUTE.
Plumb the deletion reason through the IPv6 FIB and notification paths:
- Update `fib6_del`, `fib6_del_route`, and `inet6_rt_notify` signatures
to explicitly pass the `del_reason` (u8) down the call chain.
- Update `rt6_fill_node()` to emit `RTA_DEL_REASON` attribute when the
reason is not UNSPEC.
- Record the cause in the kernel-initiated IPv6 deletion paths:
- RTA_DEL_REASON_EXPIRED: for routes cleaned up by the FIB6 garbage
collector.
- RTA_DEL_REASON_RA_WITHDRAWN: for default routes, prefix routes, or
route information option routes withdrawn by Router Advertisements.
- Update the `rt-route` Netlink YAML spec to define the new attribute,
notifications, and multicast groups.
Signed-off-by: Yuyang Huang <sigefriedhyy@gmail.com>
---
Documentation/netlink/specs/rt-route.yaml | 33 ++++++++++++
include/net/ip6_fib.h | 4 +-
include/net/ip6_route.h | 2 +
include/uapi/linux/rtnetlink.h | 17 ++++++
net/ipv6/addrconf.c | 3 +-
net/ipv6/ip6_fib.c | 19 ++++---
net/ipv6/ndisc.c | 7 ++-
net/ipv6/route.c | 66 +++++++++++++++--------
8 files changed, 116 insertions(+), 35 deletions(-)
diff --git a/Documentation/netlink/specs/rt-route.yaml b/Documentation/netlink/specs/rt-route.yaml
index 33195db96746..d5f6824127c2 100644
--- a/Documentation/netlink/specs/rt-route.yaml
+++ b/Documentation/netlink/specs/rt-route.yaml
@@ -78,6 +78,15 @@ definitions:
-
name: rta-used
type: u32
+ -
+ name: del-reason
+ type: enum
+ name-prefix: rta-del-reason-
+ enum-name: rta-del-reason
+ entries:
+ - unspec
+ - expired
+ - ra-withdrawn
attribute-sets:
-
@@ -185,6 +194,10 @@ attribute-sets:
type: u32
byte-order: big-endian
display-hint: hex
+ -
+ name: del-reason
+ type: u8
+ enum: del-reason
-
name: metrics
name-prefix: rtax-
@@ -299,6 +312,7 @@ operations:
- dport
- nh-id
- flowlabel
+ - del-reason
dump:
request:
value: 26
@@ -322,3 +336,22 @@ operations:
request:
value: 25
attributes: *all-route-attrs
+ -
+ name: newroute-ntf
+ doc: Notification about a created route.
+ value: 24
+ notify: getroute
+ -
+ name: delroute-ntf
+ doc: Notification about a deleted route.
+ value: 25
+ notify: getroute
+
+mcast-groups:
+ list:
+ -
+ name: rtnlgrp-ipv4-route
+ value: 7
+ -
+ name: rtnlgrp-ipv6-route
+ value: 11
diff --git a/include/net/ip6_fib.h b/include/net/ip6_fib.h
index 9cd27e1b9b69..c93a997bb41e 100644
--- a/include/net/ip6_fib.h
+++ b/include/net/ip6_fib.h
@@ -468,7 +468,7 @@ void fib6_clean_all_skip_notify(struct net *net,
int fib6_add(struct fib6_node *root, struct fib6_info *rt,
struct nl_info *info, struct netlink_ext_ack *extack);
-int fib6_del(struct fib6_info *rt, struct nl_info *info);
+int fib6_del(struct fib6_info *rt, struct nl_info *info, u8 del_reason);
static inline
void rt6_get_prefsrc(const struct rt6_info *rt, struct in6_addr *addr)
@@ -531,7 +531,7 @@ static inline void fib6_rt_update(struct net *net, struct fib6_info *rt,
}
#endif
void inet6_rt_notify(int event, struct fib6_info *rt, struct nl_info *info,
- unsigned int flags);
+ unsigned int flags, u8 del_reason);
void fib6_age_exceptions(struct fib6_info *rt, struct fib6_gc_args *gc_args,
unsigned long now);
diff --git a/include/net/ip6_route.h b/include/net/ip6_route.h
index 09ffe0f13ce7..bf6b39eaaa20 100644
--- a/include/net/ip6_route.h
+++ b/include/net/ip6_route.h
@@ -128,6 +128,8 @@ int ip6_route_add(struct fib6_config *cfg, gfp_t gfp_flags,
int ip6_ins_rt(struct net *net, struct fib6_info *f6i);
#if IS_ENABLED(CONFIG_IPV6)
int ip6_del_rt(struct net *net, struct fib6_info *f6i, bool skip_notify);
+int ip6_del_rt_reason(struct net *net, struct fib6_info *f6i, bool skip_notify,
+ u8 del_reason);
#else
static inline int ip6_del_rt(struct net *net, struct fib6_info *f6i,
bool skip_notify)
diff --git a/include/uapi/linux/rtnetlink.h b/include/uapi/linux/rtnetlink.h
index 27265fd31e5f..86b407bef4ce 100644
--- a/include/uapi/linux/rtnetlink.h
+++ b/include/uapi/linux/rtnetlink.h
@@ -399,6 +399,7 @@ enum rtattr_type_t {
RTA_DPORT,
RTA_NH_ID,
RTA_FLOWLABEL,
+ RTA_DEL_REASON,
__RTA_MAX
};
@@ -407,6 +408,22 @@ enum rtattr_type_t {
#define RTM_RTA(r) ((struct rtattr*)(((char*)(r)) + NLMSG_ALIGN(sizeof(struct rtmsg))))
#define RTM_PAYLOAD(n) NLMSG_PAYLOAD(n,sizeof(struct rtmsg))
+/* RTA_DEL_REASON: why the kernel deleted the route. u8.
+ * Emitted only on RTM_DELROUTE notifications, and only when the deletion
+ * path records a cause. Absence means either an older kernel or a
+ * deletion path that does not (yet) record its cause - consumers must
+ * treat "absent" and "unspec" identically. New causes may be appended.
+ * Currently only IPv6 deletion paths record a cause.
+ */
+enum rta_del_reason {
+ RTA_DEL_REASON_UNSPEC, /* cause not recorded */
+ RTA_DEL_REASON_EXPIRED, /* RTF_EXPIRES lifetime ran out (GC) */
+ RTA_DEL_REASON_RA_WITHDRAWN, /* zero-lifetime RA / PIO / RIO */
+ __RTA_DEL_REASON_MAX
+};
+
+#define RTA_DEL_REASON_MAX (__RTA_DEL_REASON_MAX - 1)
+
/* RTM_MULTIPATH --- array of struct rtnexthop.
*
* "struct rtnexthop" describes all necessary nexthop information,
diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
index f1fe9ede1edb..1ca9d82b5721 100644
--- a/net/ipv6/addrconf.c
+++ b/net/ipv6/addrconf.c
@@ -2874,7 +2874,8 @@ void addrconf_prefix_rcv(struct net_device *dev, u8 *opt, int len, bool sllao)
if (rt) {
/* Autoconf prefix route */
if (valid_lft == 0) {
- ip6_del_rt(net, rt, false);
+ ip6_del_rt_reason(net, rt, false,
+ RTA_DEL_REASON_RA_WITHDRAWN);
rt = NULL;
} else {
table = rt->fib6_table;
diff --git a/net/ipv6/ip6_fib.c b/net/ipv6/ip6_fib.c
index a130cdfaebfb..2c9bce3213b7 100644
--- a/net/ipv6/ip6_fib.c
+++ b/net/ipv6/ip6_fib.c
@@ -1286,7 +1286,8 @@ static int fib6_add_rt2node(struct fib6_node *fn, struct fib6_info *rt,
rcu_assign_pointer(rt->fib6_node, fn);
rcu_assign_pointer(*ins, rt);
if (!info->skip_notify)
- inet6_rt_notify(RTM_NEWROUTE, rt, info, nlflags);
+ inet6_rt_notify(RTM_NEWROUTE, rt, info, nlflags,
+ RTA_DEL_REASON_UNSPEC);
info->nl_net->ipv6.rt6_stats->fib_rt_entries++;
if (!(fn->fn_flags & RTN_RTINFO)) {
@@ -1317,7 +1318,8 @@ static int fib6_add_rt2node(struct fib6_node *fn, struct fib6_info *rt,
rt->fib6_next = iter->fib6_next;
rcu_assign_pointer(*ins, rt);
if (!info->skip_notify)
- inet6_rt_notify(RTM_NEWROUTE, rt, info, NLM_F_REPLACE);
+ inet6_rt_notify(RTM_NEWROUTE, rt, info, NLM_F_REPLACE,
+ RTA_DEL_REASON_UNSPEC);
if (!(fn->fn_flags & RTN_RTINFO)) {
info->nl_net->ipv6.rt6_stats->fib_route_nodes++;
fn->fn_flags |= RTN_RTINFO;
@@ -1966,7 +1968,8 @@ static struct fib6_node *fib6_repair_tree(struct net *net,
}
static void fib6_del_route(struct fib6_table *table, struct fib6_node *fn,
- struct fib6_info __rcu **rtp, struct nl_info *info)
+ struct fib6_info __rcu **rtp, struct nl_info *info,
+ u8 del_reason)
{
struct fib6_info *leaf, *replace_rt = NULL;
struct fib6_walker *w;
@@ -2055,13 +2058,13 @@ static void fib6_del_route(struct fib6_table *table, struct fib6_node *fn,
call_fib6_entry_notifiers_replace(net, replace_rt);
}
if (!info->skip_notify)
- inet6_rt_notify(RTM_DELROUTE, rt, info, 0);
+ inet6_rt_notify(RTM_DELROUTE, rt, info, 0, del_reason);
fib6_info_release(rt);
}
/* Need to own table->tb6_lock */
-int fib6_del(struct fib6_info *rt, struct nl_info *info)
+int fib6_del(struct fib6_info *rt, struct nl_info *info, u8 del_reason)
{
struct net *net = info->nl_net;
struct fib6_info __rcu **rtp;
@@ -2090,7 +2093,7 @@ int fib6_del(struct fib6_info *rt, struct nl_info *info)
if (rt == cur) {
if (fib6_requires_src(cur))
fib6_routes_require_src_dec(info->nl_net);
- fib6_del_route(table, fn, rtp, info);
+ fib6_del_route(table, fn, rtp, info, del_reason);
return 0;
}
rtp_next = &cur->fib6_next;
@@ -2252,7 +2255,7 @@ static int fib6_clean_node(struct fib6_walker *w)
res = c->func(rt, c->arg);
if (res == -1) {
w->leaf = rt;
- res = fib6_del(rt, &info);
+ res = fib6_del(rt, &info, RTA_DEL_REASON_UNSPEC);
if (res) {
#if RT6_DEBUG >= 2
pr_debug("%s: del failed: rt=%p@%p err=%d\n",
@@ -2400,7 +2403,7 @@ static void fib6_gc_table(struct net *net,
hlist_for_each_entry_safe(rt, n, &tb6->tb6_gc_hlist, gc_link)
if (fib6_age(rt, gc_args) == -1)
- fib6_del(rt, &info);
+ fib6_del(rt, &info, RTA_DEL_REASON_EXPIRED);
}
static void fib6_gc_all(struct net *net, struct fib6_gc_args *gc_args)
diff --git a/net/ipv6/ndisc.c b/net/ipv6/ndisc.c
index f867ec8d3d90..c3537fc0ec63 100644
--- a/net/ipv6/ndisc.c
+++ b/net/ipv6/ndisc.c
@@ -1361,7 +1361,9 @@ static enum skb_drop_reason ndisc_router_discovery(struct sk_buff *skb)
defrtr_usr_metric = in6_dev->cnf.ra_defrtr_metric;
/* delete the route if lifetime is 0 or if metric needs change */
if (rt && (lifetime == 0 || rt->fib6_metric != defrtr_usr_metric)) {
- ip6_del_rt(net, rt, false);
+ ip6_del_rt_reason(net, rt, false,
+ lifetime == 0 ? RTA_DEL_REASON_RA_WITHDRAWN :
+ RTA_DEL_REASON_UNSPEC);
rt = NULL;
}
@@ -1396,7 +1398,8 @@ static enum skb_drop_reason ndisc_router_discovery(struct sk_buff *skb)
.nl_net = net,
};
rt->fib6_flags = (rt->fib6_flags & ~RTF_PREF_MASK) | RTF_PREF(pref);
- inet6_rt_notify(RTM_NEWROUTE, rt, &nlinfo, NLM_F_REPLACE);
+ inet6_rt_notify(RTM_NEWROUTE, rt, &nlinfo, NLM_F_REPLACE,
+ RTA_DEL_REASON_UNSPEC);
}
if (rt) {
diff --git a/net/ipv6/route.c b/net/ipv6/route.c
index a1301334da48..ee7ba58e83c7 100644
--- a/net/ipv6/route.c
+++ b/net/ipv6/route.c
@@ -111,7 +111,7 @@ static int rt6_fill_node(struct net *net, struct sk_buff *skb,
struct fib6_info *rt, struct dst_entry *dst,
struct in6_addr *dest, struct in6_addr *src,
int iif, int type, u32 portid, u32 seq,
- unsigned int flags);
+ unsigned int flags, u8 del_reason);
static struct rt6_info *rt6_find_cached_rt(const struct fib6_result *res,
const struct in6_addr *daddr,
const struct in6_addr *saddr);
@@ -1020,7 +1020,7 @@ int rt6_route_rcv(struct net_device *dev, u8 *opt, int len,
gwaddr, dev);
if (rt && !lifetime) {
- ip6_del_rt(net, rt, false);
+ ip6_del_rt_reason(net, rt, false, RTA_DEL_REASON_RA_WITHDRAWN);
rt = NULL;
}
@@ -3973,7 +3973,8 @@ int ip6_route_add(struct fib6_config *cfg, gfp_t gfp_flags,
return err;
}
-static int __ip6_del_rt(struct fib6_info *rt, struct nl_info *info)
+static int __ip6_del_rt(struct fib6_info *rt, struct nl_info *info,
+ u8 del_reason)
{
struct net *net = info->nl_net;
struct fib6_table *table;
@@ -3986,7 +3987,7 @@ static int __ip6_del_rt(struct fib6_info *rt, struct nl_info *info)
table = rt->fib6_table;
spin_lock_bh(&table->tb6_lock);
- err = fib6_del(rt, info);
+ err = fib6_del(rt, info, del_reason);
spin_unlock_bh(&table->tb6_lock);
out:
@@ -3994,14 +3995,20 @@ static int __ip6_del_rt(struct fib6_info *rt, struct nl_info *info)
return err;
}
-int ip6_del_rt(struct net *net, struct fib6_info *rt, bool skip_notify)
+int ip6_del_rt_reason(struct net *net, struct fib6_info *rt, bool skip_notify,
+ u8 del_reason)
{
struct nl_info info = {
.nl_net = net,
- .skip_notify = skip_notify
+ .skip_notify = skip_notify,
};
- return __ip6_del_rt(rt, &info);
+ return __ip6_del_rt(rt, &info, del_reason);
+}
+
+int ip6_del_rt(struct net *net, struct fib6_info *rt, bool skip_notify)
+{
+ return ip6_del_rt_reason(net, rt, skip_notify, RTA_DEL_REASON_UNSPEC);
}
static int __ip6_del_rt_siblings(struct fib6_info *rt, struct fib6_config *cfg)
@@ -4028,7 +4035,8 @@ static int __ip6_del_rt_siblings(struct fib6_info *rt, struct fib6_config *cfg)
if (rt6_fill_node(net, skb, rt, NULL,
NULL, NULL, 0, RTM_DELROUTE,
- info->portid, seq, 0) < 0) {
+ info->portid, seq, 0,
+ RTA_DEL_REASON_UNSPEC) < 0) {
kfree_skb(skb);
skb = NULL;
} else
@@ -4064,13 +4072,13 @@ static int __ip6_del_rt_siblings(struct fib6_info *rt, struct fib6_config *cfg)
list_for_each_entry_safe(sibling, next_sibling,
&rt->fib6_siblings,
fib6_siblings) {
- err = fib6_del(sibling, info);
+ err = fib6_del(sibling, info, RTA_DEL_REASON_UNSPEC);
if (err)
goto out_unlock;
}
}
- err = fib6_del(rt, info);
+ err = fib6_del(rt, info, RTA_DEL_REASON_UNSPEC);
out_unlock:
spin_unlock_bh(&table->tb6_lock);
out_put:
@@ -4196,7 +4204,8 @@ static int ip6_route_del(struct fib6_config *cfg,
if (!fib6_info_hold_safe(rt))
continue;
- err = __ip6_del_rt(rt, &cfg->fc_nlinfo);
+ err = __ip6_del_rt(rt, &cfg->fc_nlinfo,
+ RTA_DEL_REASON_UNSPEC);
break;
}
if (cfg->fc_nh_id)
@@ -4215,7 +4224,8 @@ static int ip6_route_del(struct fib6_config *cfg,
/* if gateway was specified only delete the one hop */
if (cfg->fc_flags & RTF_GATEWAY)
- err = __ip6_del_rt(rt, &cfg->fc_nlinfo);
+ err = __ip6_del_rt(rt, &cfg->fc_nlinfo,
+ RTA_DEL_REASON_UNSPEC);
else
err = __ip6_del_rt_siblings(rt, cfg);
break;
@@ -5381,7 +5391,8 @@ static void ip6_route_mpath_notify(struct fib6_info *rt,
}
if (rt)
- inet6_rt_notify(RTM_NEWROUTE, rt, info, nlflags);
+ inet6_rt_notify(RTM_NEWROUTE, rt, info, nlflags,
+ RTA_DEL_REASON_UNSPEC);
rcu_read_unlock();
}
@@ -5739,6 +5750,7 @@ static size_t rt6_nlmsg_size(struct fib6_info *f6i)
+ nla_total_size(sizeof(struct rta_cacheinfo))
+ nla_total_size(TCP_CA_NAME_MAX) /* RTAX_CC_ALGO */
+ nla_total_size(1) /* RTA_PREF */
+ + nla_total_size(1) /* RTA_DEL_REASON */
+ nexthop_len;
}
@@ -5775,7 +5787,7 @@ static int rt6_fill_node(struct net *net, struct sk_buff *skb,
struct fib6_info *rt, struct dst_entry *dst,
struct in6_addr *dest, struct in6_addr *src,
int iif, int type, u32 portid, u32 seq,
- unsigned int flags)
+ unsigned int flags, u8 del_reason)
{
struct rt6_info *rt6 = dst_rt6_info(dst);
struct rt6key *rt6_dst, *rt6_src;
@@ -5954,6 +5966,10 @@ static int rt6_fill_node(struct net *net, struct sk_buff *skb,
if (rtnl_put_cacheinfo(skb, dst, 0, expires, dst ? dst->error : 0) < 0)
goto nla_put_failure;
+ if (type == RTM_DELROUTE && del_reason != RTA_DEL_REASON_UNSPEC &&
+ nla_put_u8(skb, RTA_DEL_REASON, del_reason))
+ goto nla_put_failure;
+
if (nla_put_u8(skb, RTA_PREF, IPV6_EXTRACT_PREF(rt6_flags)))
goto nla_put_failure;
@@ -6055,7 +6071,8 @@ static int rt6_nh_dump_exceptions(struct fib6_nh *nh, void *arg)
&rt6_ex->rt6i->dst, NULL, NULL, 0,
RTM_NEWROUTE,
NETLINK_CB(dump->cb->skb).portid,
- dump->cb->nlh->nlmsg_seq, w->flags);
+ dump->cb->nlh->nlmsg_seq, w->flags,
+ RTA_DEL_REASON_UNSPEC);
if (err)
return err;
@@ -6103,7 +6120,8 @@ int rt6_dump_route(struct fib6_info *rt, void *p_arg, unsigned int skip)
if (rt6_fill_node(net, arg->skb, rt, NULL, NULL, NULL,
0, RTM_NEWROUTE,
NETLINK_CB(arg->cb->skb).portid,
- arg->cb->nlh->nlmsg_seq, flags)) {
+ arg->cb->nlh->nlmsg_seq, flags,
+ RTA_DEL_REASON_UNSPEC)) {
return 0;
}
count++;
@@ -6336,12 +6354,14 @@ static int inet6_rtm_getroute(struct sk_buff *in_skb, struct nlmsghdr *nlh,
err = rt6_fill_node(net, skb, from, NULL, NULL, NULL,
iif, RTM_NEWROUTE,
NETLINK_CB(in_skb).portid,
- nlh->nlmsg_seq, 0);
+ nlh->nlmsg_seq, 0,
+ RTA_DEL_REASON_UNSPEC);
else
err = rt6_fill_node(net, skb, from, dst, &fl6.daddr,
&fl6.saddr, iif, RTM_NEWROUTE,
NETLINK_CB(in_skb).portid,
- nlh->nlmsg_seq, 0);
+ nlh->nlmsg_seq, 0,
+ RTA_DEL_REASON_UNSPEC);
} else {
err = -ENETUNREACH;
}
@@ -6358,7 +6378,7 @@ static int inet6_rtm_getroute(struct sk_buff *in_skb, struct nlmsghdr *nlh,
}
void inet6_rt_notify(int event, struct fib6_info *rt, struct nl_info *info,
- unsigned int nlm_flags)
+ unsigned int nlm_flags, u8 del_reason)
{
struct net *net = info->nl_net;
struct sk_buff *skb;
@@ -6377,7 +6397,8 @@ void inet6_rt_notify(int event, struct fib6_info *rt, struct nl_info *info,
goto errout;
err = rt6_fill_node(net, skb, rt, NULL, NULL, NULL, 0,
- event, info->portid, seq, nlm_flags);
+ event, info->portid, seq, nlm_flags,
+ del_reason);
if (err < 0) {
kfree_skb(skb);
/* -EMSGSIZE implies needed space grew under us. */
@@ -6410,7 +6431,8 @@ void fib6_rt_update(struct net *net, struct fib6_info *rt,
goto errout;
err = rt6_fill_node(net, skb, rt, NULL, NULL, NULL, 0,
- RTM_NEWROUTE, info->portid, seq, NLM_F_REPLACE);
+ RTM_NEWROUTE, info->portid, seq, NLM_F_REPLACE,
+ RTA_DEL_REASON_UNSPEC);
if (err < 0) {
/* -EMSGSIZE implies BUG in rt6_nlmsg_size() */
WARN_ON(err == -EMSGSIZE);
@@ -6463,7 +6485,7 @@ void fib6_info_hw_flags_set(struct net *net, struct fib6_info *f6i,
}
err = rt6_fill_node(net, skb, f6i, NULL, NULL, NULL, 0, RTM_NEWROUTE, 0,
- 0, 0);
+ 0, 0, RTA_DEL_REASON_UNSPEC);
if (err < 0) {
/* -EMSGSIZE implies BUG in rt6_nlmsg_size() */
WARN_ON(err == -EMSGSIZE);
--
2.43.0
^ permalink raw reply related [flat|nested] 3+ messages in thread
* [PATCH net-next 2/2] selftests: net: verify RTA_DEL_REASON on route deletion
2026-07-17 22:23 [PATCH net-next 0/2] ipv6: report why a route was deleted in RTM_DELROUTE Yuyang Huang
2026-07-17 22:23 ` [PATCH net-next 1/2] " Yuyang Huang
@ 2026-07-17 22:23 ` Yuyang Huang
1 sibling, 0 replies; 3+ messages in thread
From: Yuyang Huang @ 2026-07-17 22:23 UTC (permalink / raw)
To: Yuyang Huang
Cc: David S. Miller, Bobby Eshleman, Chris J Arges, Daniel Zahka,
David Ahern, David Wei, Dimitri Daskalakis, Donald Hunter,
Eric Dumazet, Gal Pressman, Ido Schimmel, Jakub Kicinski,
Paolo Abeni, Shuah Khan, Simon Horman, Stanislav Fomichev,
Willem de Bruijn, linux-kernel, linux-kselftest, netdev
Extend rtnetlink.py to check the reason reported in RTM_DELROUTE:
- expired: route with a 2s lifetime collected by the fib6 GC
(gc_interval lowered like fib_tests.sh fib6_gc_test does);
- ra-withdrawn: a single RA advertises a default route (router
lifetime), an on-link prefix route (RFC 4861 prefix information
option) and a route information option route (RFC 4191), then a
second RA withdraws all three with zero lifetimes; the RAs are
crafted over a raw ICMPv6 socket so the test does not depend on an
external RA tool;
- absence: a userspace deletion request records no cause and must not
carry the attribute at all.
Signed-off-by: Yuyang Huang <sigefriedhyy@gmail.com>
---
.../testing/selftests/net/lib/py/__init__.py | 4 +-
tools/testing/selftests/net/lib/py/ynl.py | 7 +-
tools/testing/selftests/net/rtnetlink.py | 181 +++++++++++++++++-
3 files changed, 187 insertions(+), 5 deletions(-)
diff --git a/tools/testing/selftests/net/lib/py/__init__.py b/tools/testing/selftests/net/lib/py/__init__.py
index e58bdbdc58ee..34935886b6ad 100644
--- a/tools/testing/selftests/net/lib/py/__init__.py
+++ b/tools/testing/selftests/net/lib/py/__init__.py
@@ -17,7 +17,7 @@ from .utils import CmdExitFailure, fd_read_timeout, cmd, bkg, defer, \
wait_file, tool, tc
from .bpf import bpf_map_set, bpf_map_dump, bpf_prog_map_ids
from .ynl import NlError, NlctrlFamily, YnlFamily, \
- EthtoolFamily, NetdevFamily, RtnlFamily, RtnlAddrFamily
+ EthtoolFamily, NetdevFamily, RtnlFamily, RtnlAddrFamily, RtnlRouteFamily
from .ynl import NetshaperFamily, DevlinkFamily, PSPFamily, Netlink
__all__ = ["KSRC",
@@ -34,4 +34,4 @@ __all__ = ["KSRC",
"NetdevSim", "NetdevSimDev",
"NetshaperFamily", "DevlinkFamily", "PSPFamily", "NlError",
"YnlFamily", "EthtoolFamily", "NetdevFamily", "RtnlFamily",
- "NlctrlFamily", "RtnlAddrFamily", "Netlink"]
+ "NlctrlFamily", "RtnlAddrFamily", "RtnlRouteFamily", "Netlink"]
diff --git a/tools/testing/selftests/net/lib/py/ynl.py b/tools/testing/selftests/net/lib/py/ynl.py
index 2e567062aa6c..08deff756f29 100644
--- a/tools/testing/selftests/net/lib/py/ynl.py
+++ b/tools/testing/selftests/net/lib/py/ynl.py
@@ -29,7 +29,7 @@ except ModuleNotFoundError as e:
__all__ = [
"NlError", "NlPolicy", "Netlink", "YnlFamily", "SPEC_PATH",
- "EthtoolFamily", "RtnlFamily", "RtnlAddrFamily",
+ "EthtoolFamily", "RtnlFamily", "RtnlAddrFamily", "RtnlRouteFamily",
"NetdevFamily", "NetshaperFamily", "NlctrlFamily", "DevlinkFamily",
"PSPFamily",
]
@@ -54,6 +54,11 @@ class RtnlAddrFamily(YnlFamily):
super().__init__((SPEC_PATH / Path('rt-addr.yaml')).as_posix(),
schema='', recv_size=recv_size)
+class RtnlRouteFamily(YnlFamily):
+ def __init__(self, recv_size=0):
+ super().__init__((SPEC_PATH / Path('rt-route.yaml')).as_posix(),
+ schema='', recv_size=recv_size)
+
class NetdevFamily(YnlFamily):
def __init__(self, recv_size=0):
super().__init__((SPEC_PATH / Path('netdev.yaml')).as_posix(),
diff --git a/tools/testing/selftests/net/rtnetlink.py b/tools/testing/selftests/net/rtnetlink.py
index 0c67c7c00d84..8773e88b934b 100755
--- a/tools/testing/selftests/net/rtnetlink.py
+++ b/tools/testing/selftests/net/rtnetlink.py
@@ -5,7 +5,8 @@ import socket
import struct
import time
from lib.py import bkg, ip, ksft_exit, ksft_run, ksft_eq, ksft_ge, ksft_true, KsftSkipEx
-from lib.py import CmdExitFailure, NetNS, NetNSEnter, RtnlAddrFamily
+from lib.py import ksft_not_in, ksft_not_none
+from lib.py import CmdExitFailure, NetNS, NetNSEnter, RtnlAddrFamily, RtnlRouteFamily
IPV4_ALL_HOSTS_MULTICAST = b'\xe0\x00\x00\x01'
IPV4_TEST_MULTICAST = b'\xef\x01\x01\x01'
@@ -134,8 +135,184 @@ def ipv4_devconf_notify() -> None:
ksft_true(f"inet {ifname} forwarding on" in cmd_obj.stdout,
f"No 'forwarding on' notificiation found for interface {ifname}")
+def _rtnl_route_subscribe(ns):
+ with NetNSEnter(str(ns)):
+ rtnl = RtnlRouteFamily()
+ rtnl.ntf_subscribe("rtnlgrp-ipv6-route")
+ return rtnl
+
+
+def _wait_route_ntf(rtnl, name, dst_len, dst=None, deadline=10):
+ """Return the attrs of the first matching notification, None on timeout."""
+
+ for msg in rtnl.poll_ntf(duration=deadline):
+ if msg['name'] != name:
+ continue
+ attrs = msg['msg']
+ if attrs['rtm-dst-len'] != dst_len:
+ continue
+ if dst is not None and attrs.get('dst') != dst:
+ continue
+ return attrs
+ return None
+
+
+def _collect_route_ntfs(rtnl, name, want, deadline=10):
+ """Gather attrs of matching notifications, keyed by (dst_len, dst)."""
+
+ seen = {}
+ for msg in rtnl.poll_ntf(duration=deadline):
+ if msg['name'] != name:
+ continue
+ attrs = msg['msg']
+ key = (attrs['rtm-dst-len'], attrs.get('dst'))
+ if key in want:
+ seen[key] = attrs
+ if len(seen) == len(want):
+ break
+ return seen
+
+
+def _write_ipv6_sysctl(name, value):
+ with open(f"/proc/sys/net/ipv6/{name}", "w") as f:
+ f.write(f"{value}\n")
+
+
+def ipv6_route_del_reason_expired() -> None:
+ """An expired route reports RTA_DEL_REASON == expired."""
+
+ with NetNS() as ns:
+ rtnl = _rtnl_route_subscribe(ns)
+ with NetNSEnter(str(ns)):
+ _write_ipv6_sysctl("route/gc_interval", 2)
+ ip("link add name dummy1 type dummy", ns=str(ns))
+ ip("link set dev dummy1 up", ns=str(ns))
+ ip("-6 route add 2001:db8:2::/64 dev dummy1 expires 2", ns=str(ns))
+
+ attrs = _wait_route_ntf(rtnl, 'delroute-ntf', 64, '2001:db8:2::',
+ deadline=15)
+ ksft_not_none(attrs, "no RTM_DELROUTE for the expired route")
+ if attrs is not None:
+ ksft_eq(attrs.get('del-reason'), 'expired')
+
+
+def _send_ra(sock, ifindex, lifetime, rio=None, pio=None):
+ """The kernel fills in the ICMPv6 checksum on raw ICMPv6 sockets."""
+
+ # type, code, cksum, hop limit, flags, router lifetime,
+ # reachable time, retrans timer
+ ra = struct.pack('!BBHBBHII', 134, 0, 0, 64, 0, lifetime, 0, 0)
+ if rio is not None:
+ prefix, plen, rio_lifetime = rio
+ # RFC 4191 route information option, /64 prefix (8 bytes)
+ ra += struct.pack('!BBBBI', 24, 2, plen, 0, rio_lifetime)
+ ra += socket.inet_pton(socket.AF_INET6, prefix)[:8]
+ if pio is not None:
+ prefix, plen, valid_lft = pio
+ # RFC 4861 prefix information option, on-link only (L set, A clear)
+ ra += struct.pack('!BBBBIII', 3, 4, plen, 0x80, valid_lft, 0, 0)
+ ra += socket.inet_pton(socket.AF_INET6, prefix)
+ sock.sendto(ra, ('ff02::1', 0, 0, ifindex))
+
+
+def _ra_router_sock(ns_r, ifname):
+ with NetNSEnter(str(ns_r)):
+ sock = socket.socket(socket.AF_INET6, socket.SOCK_RAW,
+ socket.IPPROTO_ICMPV6)
+ sock.setsockopt(socket.IPPROTO_IPV6, socket.IPV6_MULTICAST_HOPS, 255)
+ return sock, socket.if_nametoindex(ifname)
+
+
+def _ra_advertise_routes(rtnl, sock, ifindex, want, **ra_opts):
+ """
+ Sending fails with EADDRNOTAVAIL until the router's link-local
+ address passes DAD, so retry.
+ """
+
+ seen = {}
+ for _ in range(10):
+ try:
+ _send_ra(sock, ifindex, **ra_opts)
+ except OSError:
+ time.sleep(0.2)
+ continue
+ seen.update(_collect_route_ntfs(rtnl, 'newroute-ntf',
+ want - seen.keys(), deadline=2))
+ if len(seen) == len(want):
+ break
+ return seen
+
+
+def ipv6_route_del_reason_ra_withdrawn() -> None:
+ """
+ Routes withdrawn by a zero-lifetime RA (router lifetime, RFC 4861
+ PIO, RFC 4191 RIO) report RTA_DEL_REASON == ra-withdrawn.
+ """
+
+ # (rtm-dst-len, dst); the default route carries no RTA_DST
+ routes = {(0, None), (64, '2001:db8:6::'), (64, '2001:db8:5::')}
+
+ with NetNS() as ns_h, NetNS() as ns_r:
+ ip(f"link add veth0 netns {ns_h} type veth peer name veth1 netns {ns_r}")
+ with NetNSEnter(str(ns_h)):
+ _write_ipv6_sysctl("conf/veth0/accept_ra", 2)
+ _write_ipv6_sysctl("conf/veth0/forwarding", 0)
+ try:
+ _write_ipv6_sysctl("conf/veth0/accept_ra_rt_info_max_plen", 64)
+ except FileNotFoundError:
+ raise KsftSkipEx("no CONFIG_IPV6_ROUTE_INFO")
+ with NetNSEnter(str(ns_r)):
+ # skip DAD so the router's link-local source is usable right away
+ _write_ipv6_sysctl("conf/veth1/accept_dad", 0)
+ ip("link set dev veth0 up", ns=str(ns_h))
+ ip("link set dev veth1 up", ns=str(ns_r))
+
+ rtnl = _rtnl_route_subscribe(ns_h)
+ sock, ifindex = _ra_router_sock(ns_r, "veth1")
+
+ seen = _ra_advertise_routes(rtnl, sock, ifindex, routes,
+ lifetime=1800,
+ rio=('2001:db8:5::', 64, 600),
+ pio=('2001:db8:6::', 64, 600))
+ ksft_eq(set(seen), routes, "not all RA routes were installed")
+ if set(seen) != routes:
+ return
+
+ _send_ra(sock, ifindex, 0, rio=('2001:db8:5::', 64, 0),
+ pio=('2001:db8:6::', 64, 0))
+ seen = _collect_route_ntfs(rtnl, 'delroute-ntf', routes)
+ for key in routes:
+ attrs = seen.get(key)
+ ksft_not_none(attrs, f"no RTM_DELROUTE for {key}")
+ if attrs is not None:
+ ksft_eq(attrs.get('del-reason'), 'ra-withdrawn')
+
+
+def ipv6_route_del_reason_absent() -> None:
+ """
+ A deletion path that records no cause (here a userspace request)
+ must not carry RTA_DEL_REASON at all.
+ """
+
+ with NetNS() as ns:
+ rtnl = _rtnl_route_subscribe(ns)
+ ip("link add name dummy1 type dummy", ns=str(ns))
+ ip("link set dev dummy1 up", ns=str(ns))
+ ip("-6 route add 2001:db8:1::/64 dev dummy1", ns=str(ns))
+ ip("-6 route del 2001:db8:1::/64 dev dummy1", ns=str(ns))
+
+ attrs = _wait_route_ntf(rtnl, 'delroute-ntf', 64, '2001:db8:1::')
+ ksft_not_none(attrs, "no RTM_DELROUTE for 2001:db8:1::/64")
+ if attrs is not None:
+ ksft_not_in('del-reason', attrs,
+ "user deletion must not carry del-reason")
+
+
def main() -> None:
- ksft_run([dump_mcaddr_check, dump_mcaddr6_check, ipv4_devconf_notify])
+ ksft_run([dump_mcaddr_check, dump_mcaddr6_check, ipv4_devconf_notify,
+ ipv6_route_del_reason_expired,
+ ipv6_route_del_reason_ra_withdrawn,
+ ipv6_route_del_reason_absent])
ksft_exit()
if __name__ == "__main__":
--
2.43.0
^ permalink raw reply related [flat|nested] 3+ messages in thread
end of thread, other threads:[~2026-07-17 22:23 UTC | newest]
Thread overview: 3+ messages (download: mbox.gz follow: Atom feed
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2026-07-17 22:23 [PATCH net-next 0/2] ipv6: report why a route was deleted in RTM_DELROUTE Yuyang Huang
2026-07-17 22:23 ` [PATCH net-next 1/2] " Yuyang Huang
2026-07-17 22:23 ` [PATCH net-next 2/2] selftests: net: verify RTA_DEL_REASON on route deletion Yuyang Huang
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