[PATCH net-next 1/2] ipv4: provide addr and netconf dump consistency info

[PATCH net-next 1/2] ipv4: provide addr and netconf dump consistency info

[Nicolas Dichtel]

This patch takes benefit of dev_addr_genid and dev_base_seq to check if a change
occurs during a netlink dump. If a change is detected, the flag NLM_F_DUMP_INTR
is set in the first message after the dump was interrupted.

Reported-by: Junwei Zhang <junwei.zhang@6wind.com>
Reported-by: Hongjun Li <hongjun.li@6wind.com>
Signed-off-by: Nicolas Dichtel <nicolas.dichtel@6wind.com>
---
 net/ipv4/devinet.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/net/ipv4/devinet.c b/net/ipv4/devinet.c
index af57bba..158ca5e 100644
--- a/net/ipv4/devinet.c
+++ b/net/ipv4/devinet.c
@@ -1499,6 +1499,8 @@ static int inet_dump_ifaddr(struct sk_buff *skb, struct netlink_callback *cb)
 		idx = 0;
 		head = &net->dev_index_head[h];
 		rcu_read_lock();
+		cb->seq = atomic_read(&net->ipv4.dev_addr_genid) ^
+			  net->dev_base_seq;
 		hlist_for_each_entry_rcu(dev, head, index_hlist) {
 			if (idx < s_idx)
 				goto cont;
@@ -1519,6 +1521,7 @@ static int inet_dump_ifaddr(struct sk_buff *skb, struct netlink_callback *cb)
 					rcu_read_unlock();
 					goto done;
 				}
+				nl_dump_check_consistent(cb, nlmsg_hdr(skb));
 			}
 cont:
 			idx++;
@@ -1808,6 +1811,8 @@ static int inet_netconf_dump_devconf(struct sk_buff *skb,
 		idx = 0;
 		head = &net->dev_index_head[h];
 		rcu_read_lock();
+		cb->seq = atomic_read(&net->ipv4.dev_addr_genid) ^
+			  net->dev_base_seq;
 		hlist_for_each_entry_rcu(dev, head, index_hlist) {
 			if (idx < s_idx)
 				goto cont;
@@ -1825,6 +1830,7 @@ static int inet_netconf_dump_devconf(struct sk_buff *skb,
 				rcu_read_unlock();
 				goto done;
 			}
+			nl_dump_check_consistent(cb, nlmsg_hdr(skb));
 cont:
 			idx++;
 		}
-- 
1.8.0.1

[PATCH net-next 2/2] ipv6: provide addr and netconf dump consistency info

[Nicolas Dichtel]

This patch adds a dev_addr_genid for IPv6. The goal is to use it, combined with
dev_base_seq to check if a change occurs during a netlink dump.
If a change is detected, the flag NLM_F_DUMP_INTR is set in the first message
after the dump was interrupted.

Note that only dump of unicast addresses is checked (multicast and anycast are
not checked).

Reported-by: Junwei Zhang <junwei.zhang@6wind.com>
Reported-by: Hongjun Li <hongjun.li@6wind.com>
Signed-off-by: Nicolas Dichtel <nicolas.dichtel@6wind.com>
---
 include/net/netns/ipv6.h | 1 +
 net/ipv6/addrconf.c      | 8 ++++++++
 2 files changed, 9 insertions(+)

diff --git a/include/net/netns/ipv6.h b/include/net/netns/ipv6.h
index 1242f37..005e2c2 100644
--- a/include/net/netns/ipv6.h
+++ b/include/net/netns/ipv6.h
@@ -71,6 +71,7 @@ struct netns_ipv6 {
 	struct fib_rules_ops	*mr6_rules_ops;
 #endif
 #endif
+	atomic_t		dev_addr_genid;
 };
 
 #if IS_ENABLED(CONFIG_NF_DEFRAG_IPV6)
diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
index fa36a67..d0e40d4 100644
--- a/net/ipv6/addrconf.c
+++ b/net/ipv6/addrconf.c
@@ -622,6 +622,8 @@ static int inet6_netconf_dump_devconf(struct sk_buff *skb,
 		idx = 0;
 		head = &net->dev_index_head[h];
 		rcu_read_lock();
+		cb->seq = atomic_read(&net->ipv6.dev_addr_genid) ^
+			  net->dev_base_seq;
 		hlist_for_each_entry_rcu(dev, head, index_hlist) {
 			if (idx < s_idx)
 				goto cont;
@@ -639,6 +641,7 @@ static int inet6_netconf_dump_devconf(struct sk_buff *skb,
 				rcu_read_unlock();
 				goto done;
 			}
+			nl_dump_check_consistent(cb, nlmsg_hdr(skb));
 cont:
 			idx++;
 		}
@@ -3875,6 +3878,7 @@ static int in6_dump_addrs(struct inet6_dev *idev, struct sk_buff *skb,
 						NLM_F_MULTI);
 			if (err <= 0)
 				break;
+			nl_dump_check_consistent(cb, nlmsg_hdr(skb));
 		}
 		break;
 	}
@@ -3932,6 +3936,7 @@ static int inet6_dump_addr(struct sk_buff *skb, struct netlink_callback *cb,
 	s_ip_idx = ip_idx = cb->args[2];
 
 	rcu_read_lock();
+	cb->seq = atomic_read(&net->ipv6.dev_addr_genid) ^ net->dev_base_seq;
 	for (h = s_h; h < NETDEV_HASHENTRIES; h++, s_idx = 0) {
 		idx = 0;
 		head = &net->dev_index_head[h];
@@ -4409,6 +4414,8 @@ errout:
 
 static void __ipv6_ifa_notify(int event, struct inet6_ifaddr *ifp)
 {
+	struct net *net = dev_net(ifp->idev->dev);
+
 	inet6_ifa_notify(event ? : RTM_NEWADDR, ifp);
 
 	switch (event) {
@@ -4434,6 +4441,7 @@ static void __ipv6_ifa_notify(int event, struct inet6_ifaddr *ifp)
 			dst_free(&ifp->rt->dst);
 		break;
 	}
+	atomic_inc(&net->ipv6.dev_addr_genid);
 }
 
 static void ipv6_ifa_notify(int event, struct inet6_ifaddr *ifp)
-- 
1.8.0.1

Re: [PATCH net-next 2/2] ipv6: provide addr and netconf dump consistency info

[Nicolas Dichtel]

Please, drop both patches. If we dump addresses via rtnl_dump_all(), seq is not 
reset and thus NLM_F_DUMP_INTR is always set when switching from ipv4 to ipv6 
family.

I will send a new patch.

Nicolas

Le 22/03/2013 15:42, Nicolas Dichtel a écrit :
> This patch adds a dev_addr_genid for IPv6. The goal is to use it, combined with
> dev_base_seq to check if a change occurs during a netlink dump.
> If a change is detected, the flag NLM_F_DUMP_INTR is set in the first message
> after the dump was interrupted.
>
> Note that only dump of unicast addresses is checked (multicast and anycast are
> not checked).
>
> Reported-by: Junwei Zhang <junwei.zhang@6wind.com>
> Reported-by: Hongjun Li <hongjun.li@6wind.com>
> Signed-off-by: Nicolas Dichtel <nicolas.dichtel@6wind.com>
> ---
>   include/net/netns/ipv6.h | 1 +
>   net/ipv6/addrconf.c      | 8 ++++++++
>   2 files changed, 9 insertions(+)
>
> diff --git a/include/net/netns/ipv6.h b/include/net/netns/ipv6.h
> index 1242f37..005e2c2 100644
> --- a/include/net/netns/ipv6.h
> +++ b/include/net/netns/ipv6.h
> @@ -71,6 +71,7 @@ struct netns_ipv6 {
>   	struct fib_rules_ops	*mr6_rules_ops;
>   #endif
>   #endif
> +	atomic_t		dev_addr_genid;
>   };
>
>   #if IS_ENABLED(CONFIG_NF_DEFRAG_IPV6)
> diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
> index fa36a67..d0e40d4 100644
> --- a/net/ipv6/addrconf.c
> +++ b/net/ipv6/addrconf.c
> @@ -622,6 +622,8 @@ static int inet6_netconf_dump_devconf(struct sk_buff *skb,
>   		idx = 0;
>   		head = &net->dev_index_head[h];
>   		rcu_read_lock();
> +		cb->seq = atomic_read(&net->ipv6.dev_addr_genid) ^
> +			  net->dev_base_seq;
>   		hlist_for_each_entry_rcu(dev, head, index_hlist) {
>   			if (idx < s_idx)
>   				goto cont;
> @@ -639,6 +641,7 @@ static int inet6_netconf_dump_devconf(struct sk_buff *skb,
>   				rcu_read_unlock();
>   				goto done;
>   			}
> +			nl_dump_check_consistent(cb, nlmsg_hdr(skb));
>   cont:
>   			idx++;
>   		}
> @@ -3875,6 +3878,7 @@ static int in6_dump_addrs(struct inet6_dev *idev, struct sk_buff *skb,
>   						NLM_F_MULTI);
>   			if (err <= 0)
>   				break;
> +			nl_dump_check_consistent(cb, nlmsg_hdr(skb));
>   		}
>   		break;
>   	}
> @@ -3932,6 +3936,7 @@ static int inet6_dump_addr(struct sk_buff *skb, struct netlink_callback *cb,
>   	s_ip_idx = ip_idx = cb->args[2];
>
>   	rcu_read_lock();
> +	cb->seq = atomic_read(&net->ipv6.dev_addr_genid) ^ net->dev_base_seq;
>   	for (h = s_h; h < NETDEV_HASHENTRIES; h++, s_idx = 0) {
>   		idx = 0;
>   		head = &net->dev_index_head[h];
> @@ -4409,6 +4414,8 @@ errout:
>
>   static void __ipv6_ifa_notify(int event, struct inet6_ifaddr *ifp)
>   {
> +	struct net *net = dev_net(ifp->idev->dev);
> +
>   	inet6_ifa_notify(event ? : RTM_NEWADDR, ifp);
>
>   	switch (event) {
> @@ -4434,6 +4441,7 @@ static void __ipv6_ifa_notify(int event, struct inet6_ifaddr *ifp)
>   			dst_free(&ifp->rt->dst);
>   		break;
>   	}
> +	atomic_inc(&net->ipv6.dev_addr_genid);
>   }
>
>   static void ipv6_ifa_notify(int event, struct inet6_ifaddr *ifp)
>

-- 
Nicolas DICHTEL
6WIND
R&D Engineer

Tel: +33 1 39 30 92 41
Fax: +33 1 39 30 92 11
nicolas.dichtel@6wind.com
www.6wind.com
www.6windblog.com
Twitter: http://twitter.com/6windsoftware

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[PATCH net-next v2 1/2] ipv4: provide addr and netconf dump consistency info

[Nicolas Dichtel]

This patch takes benefit of dev_addr_genid and dev_base_seq to check if a change
occurs during a netlink dump. If a change is detected, the flag NLM_F_DUMP_INTR
is set in the first message after the dump was interrupted.

Note that seq and prev_seq must be reset between each family in rtnl_dump_all()
because they are specific to each family.

Reported-by: Junwei Zhang <junwei.zhang@6wind.com>
Reported-by: Hongjun Li <hongjun.li@6wind.com>
Signed-off-by: Nicolas Dichtel <nicolas.dichtel@6wind.com>
---

v2: reset seq and prev_seq in rtnl_dump_all()

 net/core/rtnetlink.c | 5 ++++-
 net/ipv4/devinet.c   | 6 ++++++
 2 files changed, 10 insertions(+), 1 deletion(-)

diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c
index 9a9b99e..4493d7a 100644
--- a/net/core/rtnetlink.c
+++ b/net/core/rtnetlink.c
@@ -1955,8 +1955,11 @@ static int rtnl_dump_all(struct sk_buff *skb, struct netlink_callback *cb)
 		if (rtnl_msg_handlers[idx] == NULL ||
 		    rtnl_msg_handlers[idx][type].dumpit == NULL)
 			continue;
-		if (idx > s_idx)
+		if (idx > s_idx) {
 			memset(&cb->args[0], 0, sizeof(cb->args));
+			cb->prev_seq = 0;
+			cb->seq = 0;
+		}
 		if (rtnl_msg_handlers[idx][type].dumpit(skb, cb))
 			break;
 	}
diff --git a/net/ipv4/devinet.c b/net/ipv4/devinet.c
index af57bba..158ca5e 100644
--- a/net/ipv4/devinet.c
+++ b/net/ipv4/devinet.c
@@ -1499,6 +1499,8 @@ static int inet_dump_ifaddr(struct sk_buff *skb, struct netlink_callback *cb)
 		idx = 0;
 		head = &net->dev_index_head[h];
 		rcu_read_lock();
+		cb->seq = atomic_read(&net->ipv4.dev_addr_genid) ^
+			  net->dev_base_seq;
 		hlist_for_each_entry_rcu(dev, head, index_hlist) {
 			if (idx < s_idx)
 				goto cont;
@@ -1519,6 +1521,7 @@ static int inet_dump_ifaddr(struct sk_buff *skb, struct netlink_callback *cb)
 					rcu_read_unlock();
 					goto done;
 				}
+				nl_dump_check_consistent(cb, nlmsg_hdr(skb));
 			}
 cont:
 			idx++;
@@ -1808,6 +1811,8 @@ static int inet_netconf_dump_devconf(struct sk_buff *skb,
 		idx = 0;
 		head = &net->dev_index_head[h];
 		rcu_read_lock();
+		cb->seq = atomic_read(&net->ipv4.dev_addr_genid) ^
+			  net->dev_base_seq;
 		hlist_for_each_entry_rcu(dev, head, index_hlist) {
 			if (idx < s_idx)
 				goto cont;
@@ -1825,6 +1830,7 @@ static int inet_netconf_dump_devconf(struct sk_buff *skb,
 				rcu_read_unlock();
 				goto done;
 			}
+			nl_dump_check_consistent(cb, nlmsg_hdr(skb));
 cont:
 			idx++;
 		}
-- 
1.8.0.1

[PATCH net-next v2 2/2] ipv6: provide addr and netconf dump consistency info

[Nicolas Dichtel]

This patch adds a dev_addr_genid for IPv6. The goal is to use it, combined with
dev_base_seq to check if a change occurs during a netlink dump.
If a change is detected, the flag NLM_F_DUMP_INTR is set in the first message
after the dump was interrupted.

Note that only dump of unicast addresses is checked (multicast and anycast are
not checked).

Reported-by: Junwei Zhang <junwei.zhang@6wind.com>
Reported-by: Hongjun Li <hongjun.li@6wind.com>
Signed-off-by: Nicolas Dichtel <nicolas.dichtel@6wind.com>
---
 include/net/netns/ipv6.h | 1 +
 net/ipv6/addrconf.c      | 8 ++++++++
 2 files changed, 9 insertions(+)

diff --git a/include/net/netns/ipv6.h b/include/net/netns/ipv6.h
index 1242f37..005e2c2 100644
--- a/include/net/netns/ipv6.h
+++ b/include/net/netns/ipv6.h
@@ -71,6 +71,7 @@ struct netns_ipv6 {
 	struct fib_rules_ops	*mr6_rules_ops;
 #endif
 #endif
+	atomic_t		dev_addr_genid;
 };
 
 #if IS_ENABLED(CONFIG_NF_DEFRAG_IPV6)
diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
index fa36a67..d0e40d4 100644
--- a/net/ipv6/addrconf.c
+++ b/net/ipv6/addrconf.c
@@ -622,6 +622,8 @@ static int inet6_netconf_dump_devconf(struct sk_buff *skb,
 		idx = 0;
 		head = &net->dev_index_head[h];
 		rcu_read_lock();
+		cb->seq = atomic_read(&net->ipv6.dev_addr_genid) ^
+			  net->dev_base_seq;
 		hlist_for_each_entry_rcu(dev, head, index_hlist) {
 			if (idx < s_idx)
 				goto cont;
@@ -639,6 +641,7 @@ static int inet6_netconf_dump_devconf(struct sk_buff *skb,
 				rcu_read_unlock();
 				goto done;
 			}
+			nl_dump_check_consistent(cb, nlmsg_hdr(skb));
 cont:
 			idx++;
 		}
@@ -3875,6 +3878,7 @@ static int in6_dump_addrs(struct inet6_dev *idev, struct sk_buff *skb,
 						NLM_F_MULTI);
 			if (err <= 0)
 				break;
+			nl_dump_check_consistent(cb, nlmsg_hdr(skb));
 		}
 		break;
 	}
@@ -3932,6 +3936,7 @@ static int inet6_dump_addr(struct sk_buff *skb, struct netlink_callback *cb,
 	s_ip_idx = ip_idx = cb->args[2];
 
 	rcu_read_lock();
+	cb->seq = atomic_read(&net->ipv6.dev_addr_genid) ^ net->dev_base_seq;
 	for (h = s_h; h < NETDEV_HASHENTRIES; h++, s_idx = 0) {
 		idx = 0;
 		head = &net->dev_index_head[h];
@@ -4409,6 +4414,8 @@ errout:
 
 static void __ipv6_ifa_notify(int event, struct inet6_ifaddr *ifp)
 {
+	struct net *net = dev_net(ifp->idev->dev);
+
 	inet6_ifa_notify(event ? : RTM_NEWADDR, ifp);
 
 	switch (event) {
@@ -4434,6 +4441,7 @@ static void __ipv6_ifa_notify(int event, struct inet6_ifaddr *ifp)
 			dst_free(&ifp->rt->dst);
 		break;
 	}
+	atomic_inc(&net->ipv6.dev_addr_genid);
 }
 
 static void ipv6_ifa_notify(int event, struct inet6_ifaddr *ifp)
-- 
1.8.0.1

Re: [PATCH net-next v2 1/2] ipv4: provide addr and netconf dump consistency info

[David Miller]

From: Nicolas Dichtel <nicolas.dichtel@6wind.com>
Date: Fri, 22 Mar 2013 17:28:42 +0100

> This patch takes benefit of dev_addr_genid and dev_base_seq to check if a change
> occurs during a netlink dump. If a change is detected, the flag NLM_F_DUMP_INTR
> is set in the first message after the dump was interrupted.
> 
> Note that seq and prev_seq must be reset between each family in rtnl_dump_all()
> because they are specific to each family.
> 
> Reported-by: Junwei Zhang <junwei.zhang@6wind.com>
> Reported-by: Hongjun Li <hongjun.li@6wind.com>
> Signed-off-by: Nicolas Dichtel <nicolas.dichtel@6wind.com>

Applied.

[PATCH iproute2] libnetlink: check flag NLM_F_DUMP_INTR during dumps

[Nicolas Dichtel]

When this flag is set, it means that dump was interrupted and result may be
wrong. Ask user to restart.

Signed-off-by: Nicolas Dichtel <nicolas.dichtel@6wind.com>
---
 lib/libnetlink.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/lib/libnetlink.c b/lib/libnetlink.c
index f262959..91991cf 100644
--- a/lib/libnetlink.c
+++ b/lib/libnetlink.c
@@ -230,6 +230,12 @@ int rtnl_dump_filter_l(struct rtnl_handle *rth,
 				    h->nlmsg_seq != rth->dump)
 					goto skip_it;
 
+				if (h->nlmsg_flags & NLM_F_DUMP_INTR) {
+					fprintf(stderr,
+						"Dump was interrupted, please restart.\n");
+					return -1;
+				}
+
 				if (h->nlmsg_type == NLMSG_DONE) {
 					found_done = 1;
 					break; /* process next filter */
-- 
1.8.0.1

Re: [PATCH iproute2] libnetlink: check flag NLM_F_DUMP_INTR during dumps

[Eric Dumazet]

On Fri, 2013-03-22 at 15:45 +0100, Nicolas Dichtel wrote:
> When this flag is set, it means that dump was interrupted and result may be
> wrong. Ask user to restart.
> 
> Signed-off-by: Nicolas Dichtel <nicolas.dichtel@6wind.com>


Do we have a guarantee this will complete eventually, on some hosts
constantly adding removing entries ?

Re: [PATCH iproute2] libnetlink: check flag NLM_F_DUMP_INTR during dumps

[Nicolas Dichtel]

Le 22/03/2013 15:59, Eric Dumazet a écrit :
> On Fri, 2013-03-22 at 15:45 +0100, Nicolas Dichtel wrote:
>> When this flag is set, it means that dump was interrupted and result may be
>> wrong. Ask user to restart.
>>
>> Signed-off-by: Nicolas Dichtel <nicolas.dichtel@6wind.com>
>
>
> Do we have a guarantee this will complete eventually, on some hosts
> constantly adding removing entries ?
>

No. You mean it will be better to just print a warning and continue the dump?

Re: [PATCH iproute2] libnetlink: check flag NLM_F_DUMP_INTR during dumps

[Eric Dumazet]

On Fri, 2013-03-22 at 16:03 +0100, Nicolas Dichtel wrote:
> Le 22/03/2013 15:59, Eric Dumazet a écrit :
> > On Fri, 2013-03-22 at 15:45 +0100, Nicolas Dichtel wrote:
> >> When this flag is set, it means that dump was interrupted and result may be
> >> wrong. Ask user to restart.
> >>
> >> Signed-off-by: Nicolas Dichtel <nicolas.dichtel@6wind.com>
> >
> >
> > Do we have a guarantee this will complete eventually, on some hosts
> > constantly adding removing entries ?
> >
> 
> No. You mean it will be better to just print a warning and continue the dump?
> --

I would not break the dump, return the indication, so that caller can
chose to restart the loop one or two times.

Re: [PATCH iproute2] libnetlink: check flag NLM_F_DUMP_INTR during dumps

[Thomas Graf]

On 03/22/13 at 08:14am, Eric Dumazet wrote:
> On Fri, 2013-03-22 at 16:03 +0100, Nicolas Dichtel wrote:
> > Le 22/03/2013 15:59, Eric Dumazet a écrit :
> > > On Fri, 2013-03-22 at 15:45 +0100, Nicolas Dichtel wrote:
> > >> When this flag is set, it means that dump was interrupted and result may be
> > >> wrong. Ask user to restart.
> > >>
> > >> Signed-off-by: Nicolas Dichtel <nicolas.dichtel@6wind.com>
> > >
> > >
> > > Do we have a guarantee this will complete eventually, on some hosts
> > > constantly adding removing entries ?
> > >
> > 
> > No. You mean it will be better to just print a warning and continue the dump?
> 
> I would not break the dump, return the indication, so that caller can
> chose to restart the loop one or two times.

Right, I would do it on an informal level at first. In fact libnl
will do an automatic restart of cache refills but I'm considering
to make it configurable for the application.

[PATCH iproute2 v2] libnetlink: check flag NLM_F_DUMP_INTR during dumps

[Nicolas Dichtel]

When this flag is set, it means that dump was interrupted and result may be
wrong. Inform the user and let him choose to restart or not.

Signed-off-by: Nicolas Dichtel <nicolas.dichtel@6wind.com>
---

v2: do not stop the dump, only display a warning

 lib/libnetlink.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/lib/libnetlink.c b/lib/libnetlink.c
index f262959..1a882b2 100644
--- a/lib/libnetlink.c
+++ b/lib/libnetlink.c
@@ -230,6 +230,10 @@ int rtnl_dump_filter_l(struct rtnl_handle *rth,
 				    h->nlmsg_seq != rth->dump)
 					goto skip_it;
 
+				if (h->nlmsg_flags & NLM_F_DUMP_INTR)
+					fprintf(stderr,
+						"Dump was interrupted and may be wrong.\n");
+
 				if (h->nlmsg_type == NLMSG_DONE) {
 					found_done = 1;
 					break; /* process next filter */
-- 
1.8.0.1

Re: [PATCH iproute2 v2] libnetlink: check flag NLM_F_DUMP_INTR during dumps

[Eric Dumazet]

On Fri, 2013-03-22 at 16:42 +0100, Nicolas Dichtel wrote:
> When this flag is set, it means that dump was interrupted and result may be
> wrong. Inform the user and let him choose to restart or not.
> 
> Signed-off-by: Nicolas Dichtel <nicolas.dichtel@6wind.com>
> ---
> 
> v2: do not stop the dump, only display a warning
> 
>  lib/libnetlink.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/lib/libnetlink.c b/lib/libnetlink.c
> index f262959..1a882b2 100644
> --- a/lib/libnetlink.c
> +++ b/lib/libnetlink.c
> @@ -230,6 +230,10 @@ int rtnl_dump_filter_l(struct rtnl_handle *rth,
>  				    h->nlmsg_seq != rth->dump)
>  					goto skip_it;
>  
> +				if (h->nlmsg_flags & NLM_F_DUMP_INTR)
> +					fprintf(stderr,
> +						"Dump was interrupted and may be wrong.\n");
> +
>  				if (h->nlmsg_type == NLMSG_DONE) {
>  					found_done = 1;
>  					break; /* process next filter */


How many times this will be displayed ?

Please try to cook something that wont emit one warning per 8KB fetched
from the kernel ;)

[PATCH iproute2 v3] libnetlink: check flag NLM_F_DUMP_INTR during dumps

[Nicolas Dichtel]

When this flag is set, it means that dump was interrupted and result may be
inconsistent.

Signed-off-by: Nicolas Dichtel <nicolas.dichtel@6wind.com>
---

v3: display the warning only once
v2: do not stop the dump, only display a warning

 lib/libnetlink.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/lib/libnetlink.c b/lib/libnetlink.c
index f262959..04201cd 100644
--- a/lib/libnetlink.c
+++ b/lib/libnetlink.c
@@ -194,6 +194,7 @@ int rtnl_dump_filter_l(struct rtnl_handle *rth,
 		.msg_iovlen = 1,
 	};
 	char buf[16384];
+	int dump_intr = 0;
 
 	iov.iov_base = buf;
 	while (1) {
@@ -230,6 +231,9 @@ int rtnl_dump_filter_l(struct rtnl_handle *rth,
 				    h->nlmsg_seq != rth->dump)
 					goto skip_it;
 
+				if (h->nlmsg_flags & NLM_F_DUMP_INTR)
+					dump_intr = 1;
+
 				if (h->nlmsg_type == NLMSG_DONE) {
 					found_done = 1;
 					break; /* process next filter */
@@ -254,8 +258,12 @@ skip_it:
 			}
 		}
 
-		if (found_done)
+		if (found_done) {
+			if (dump_intr)
+				fprintf(stderr,
+					"Dump was interrupted and may be inconsistent.\n");
 			return 0;
+		}
 
 		if (msg.msg_flags & MSG_TRUNC) {
 			fprintf(stderr, "Message truncated\n");
-- 
1.8.0.1

Re: [PATCH net-next v2 2/2] ipv6: provide addr and netconf dump consistency info

[David Miller]

From: Nicolas Dichtel <nicolas.dichtel@6wind.com>
Date: Fri, 22 Mar 2013 17:34:02 +0100

> When this flag is set, it means that dump was interrupted and result may be
> inconsistent.
> 
> Signed-off-by: Nicolas Dichtel <nicolas.dichtel@6wind.com>

Applied.