diff mbox series

[net-next,v6] ipv6: add IFLA_INET6_RA_MTU to expose mtu value

Message ID 20210827150412.9267-1-rocco.yue@mediatek.com
State New
Headers show
Series [net-next,v6] ipv6: add IFLA_INET6_RA_MTU to expose mtu value | expand

Commit Message

Rocco Yue Aug. 27, 2021, 3:04 p.m. UTC 
The kernel provides a "/proc/sys/net/ipv6/conf/<iface>/mtu"
file, which can temporarily record the mtu value of the last
received RA message when the RA mtu value is lower than the
interface mtu, but this proc has following limitations:

(1) when the interface mtu (/sys/class/net/<iface>/mtu) is
updeated, mtu6 (/proc/sys/net/ipv6/conf/<iface>/mtu) will
be updated to the value of interface mtu;
(2) mtu6 (/proc/sys/net/ipv6/conf/<iface>/mtu) only affect
ipv6 connection, and not affect ipv4.

Therefore, when the mtu option is carried in the RA message,
there will be a problem that the user sometimes cannot obtain
RA mtu value correctly by reading mtu6.

After this patch set, if a RA message carries the mtu option,
you can send a netlink msg which nlmsg_type is RTM_GETLINK,
and then by parsing the attribute of IFLA_INET6_RA_MTU to
get the mtu value carried in the RA message received on the
inet6 device. In addition, you can also get a link notification
when ra_mtu is updated so it doesn't have to poll.

In this way, if the MTU values that the device receives from
the network in the PCO IPv4 and the RA IPv6 procedures are
different, the user can obtain the correct ipv6 ra_mtu value
and compare the value of ra_mtu and ipv4 mtu, then the device
can use the lower MTU value for both IPv4 and IPv6.

Signed-off-by: Rocco Yue <rocco.yue@mediatek.com>
---
 include/net/if_inet6.h             |  2 ++
 include/uapi/linux/if_link.h       |  1 +
 net/ipv6/addrconf.c                | 10 ++++++++++
 net/ipv6/ndisc.c                   | 17 +++++++++++------
 tools/include/uapi/linux/if_link.h |  1 +
 5 files changed, 25 insertions(+), 6 deletions(-)

Comments

Jakub Kicinski Aug. 28, 2021, 4:06 a.m. UTC | #1 
On Fri, 27 Aug 2021 09:41:53 -0700 David Ahern wrote:
> On 8/27/21 8:04 AM, Rocco Yue wrote:
> > The kernel provides a "/proc/sys/net/ipv6/conf/<iface>/mtu"
> > file, which can temporarily record the mtu value of the last
> > received RA message when the RA mtu value is lower than the
> > interface mtu, but this proc has following limitations:
> > 
> > (1) when the interface mtu (/sys/class/net/<iface>/mtu) is
> > updeated, mtu6 (/proc/sys/net/ipv6/conf/<iface>/mtu) will
> > be updated to the value of interface mtu;
> > (2) mtu6 (/proc/sys/net/ipv6/conf/<iface>/mtu) only affect
> > ipv6 connection, and not affect ipv4.
> > 
> > Therefore, when the mtu option is carried in the RA message,
> > there will be a problem that the user sometimes cannot obtain
> > RA mtu value correctly by reading mtu6.
> > 
> > After this patch set, if a RA message carries the mtu option,
> > you can send a netlink msg which nlmsg_type is RTM_GETLINK,
> > and then by parsing the attribute of IFLA_INET6_RA_MTU to
> > get the mtu value carried in the RA message received on the
> > inet6 device. In addition, you can also get a link notification
> > when ra_mtu is updated so it doesn't have to poll.
> > 
> > In this way, if the MTU values that the device receives from
> > the network in the PCO IPv4 and the RA IPv6 procedures are
> > different, the user can obtain the correct ipv6 ra_mtu value
> > and compare the value of ra_mtu and ipv4 mtu, then the device
> > can use the lower MTU value for both IPv4 and IPv6.
> > 
> > Signed-off-by: Rocco Yue <rocco.yue@mediatek.com>
>
> Reviewed-by: David Ahern <dsahern@kernel.org>

Applied, thank you!
diff mbox series

Patch

diff --git a/include/net/if_inet6.h b/include/net/if_inet6.h
index 42235c178b06..653e7d0f65cb 100644
--- a/include/net/if_inet6.h
+++ b/include/net/if_inet6.h
@@ -210,6 +210,8 @@  struct inet6_dev {
 
 	unsigned long		tstamp; /* ipv6InterfaceTable update timestamp */
 	struct rcu_head		rcu;
+
+	unsigned int		ra_mtu;
 };
 
 static inline void ipv6_eth_mc_map(const struct in6_addr *addr, char *buf)
diff --git a/include/uapi/linux/if_link.h b/include/uapi/linux/if_link.h
index 8aad65b69054..eebd3894fe89 100644
--- a/include/uapi/linux/if_link.h
+++ b/include/uapi/linux/if_link.h
@@ -417,6 +417,7 @@  enum {
 	IFLA_INET6_ICMP6STATS,	/* statistics (icmpv6)		*/
 	IFLA_INET6_TOKEN,	/* device token			*/
 	IFLA_INET6_ADDR_GEN_MODE, /* implicit address generator mode */
+	IFLA_INET6_RA_MTU,	/* mtu carried in the RA message */
 	__IFLA_INET6_MAX
 };
 
diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
index 8381288a0d6e..17756f3ed33b 100644
--- a/net/ipv6/addrconf.c
+++ b/net/ipv6/addrconf.c
@@ -394,6 +394,7 @@  static struct inet6_dev *ipv6_add_dev(struct net_device *dev)
 		ndev->cnf.addr_gen_mode = IN6_ADDR_GEN_MODE_STABLE_PRIVACY;
 
 	ndev->cnf.mtu6 = dev->mtu;
+	ndev->ra_mtu = 0;
 	ndev->nd_parms = neigh_parms_alloc(dev, &nd_tbl);
 	if (!ndev->nd_parms) {
 		kfree(ndev);
@@ -3849,6 +3850,7 @@  static int addrconf_ifdown(struct net_device *dev, bool unregister)
 	}
 
 	idev->tstamp = jiffies;
+	idev->ra_mtu = 0;
 
 	/* Last: Shot the device (if unregistered) */
 	if (unregister) {
@@ -5543,6 +5545,7 @@  static inline size_t inet6_ifla6_size(void)
 	     + nla_total_size(ICMP6_MIB_MAX * 8) /* IFLA_INET6_ICMP6STATS */
 	     + nla_total_size(sizeof(struct in6_addr)) /* IFLA_INET6_TOKEN */
 	     + nla_total_size(1) /* IFLA_INET6_ADDR_GEN_MODE */
+	     + nla_total_size(4) /* IFLA_INET6_RA_MTU */
 	     + 0;
 }
 
@@ -5651,6 +5654,10 @@  static int inet6_fill_ifla6_attrs(struct sk_buff *skb, struct inet6_dev *idev,
 	if (nla_put_u8(skb, IFLA_INET6_ADDR_GEN_MODE, idev->cnf.addr_gen_mode))
 		goto nla_put_failure;
 
+	if (idev->ra_mtu &&
+	    nla_put_u32(skb, IFLA_INET6_RA_MTU, idev->ra_mtu))
+		goto nla_put_failure;
+
 	return 0;
 
 nla_put_failure:
@@ -5767,6 +5774,9 @@  static int inet6_set_iftoken(struct inet6_dev *idev, struct in6_addr *token,
 static const struct nla_policy inet6_af_policy[IFLA_INET6_MAX + 1] = {
 	[IFLA_INET6_ADDR_GEN_MODE]	= { .type = NLA_U8 },
 	[IFLA_INET6_TOKEN]		= { .len = sizeof(struct in6_addr) },
+	[IFLA_INET6_RA_MTU]		= { .type = NLA_REJECT,
+					    .reject_message =
+						"IFLA_INET6_RA_MTU can not be set" },
 };
 
 static int check_addr_gen_mode(int mode)
diff --git a/net/ipv6/ndisc.c b/net/ipv6/ndisc.c
index c467c6419893..4b098521a44c 100644
--- a/net/ipv6/ndisc.c
+++ b/net/ipv6/ndisc.c
@@ -1391,12 +1391,6 @@  static void ndisc_router_discovery(struct sk_buff *skb)
 		}
 	}
 
-	/*
-	 *	Send a notify if RA changed managed/otherconf flags or timer settings
-	 */
-	if (send_ifinfo_notify)
-		inet6_ifinfo_notify(RTM_NEWLINK, in6_dev);
-
 skip_linkparms:
 
 	/*
@@ -1496,6 +1490,11 @@  static void ndisc_router_discovery(struct sk_buff *skb)
 		memcpy(&n, ((u8 *)(ndopts.nd_opts_mtu+1))+2, sizeof(mtu));
 		mtu = ntohl(n);
 
+		if (in6_dev->ra_mtu != mtu) {
+			in6_dev->ra_mtu = mtu;
+			send_ifinfo_notify = true;
+		}
+
 		if (mtu < IPV6_MIN_MTU || mtu > skb->dev->mtu) {
 			ND_PRINTK(2, warn, "RA: invalid mtu: %d\n", mtu);
 		} else if (in6_dev->cnf.mtu6 != mtu) {
@@ -1519,6 +1518,12 @@  static void ndisc_router_discovery(struct sk_buff *skb)
 		ND_PRINTK(2, warn, "RA: invalid RA options\n");
 	}
 out:
+	/* Send a notify if RA changed managed/otherconf flags or
+	 * timer settings or ra_mtu value
+	 */
+	if (send_ifinfo_notify)
+		inet6_ifinfo_notify(RTM_NEWLINK, in6_dev);
+
 	fib6_info_release(rt);
 	if (neigh)
 		neigh_release(neigh);
diff --git a/tools/include/uapi/linux/if_link.h b/tools/include/uapi/linux/if_link.h
index eb15f319aa57..b3610fdd1fee 100644
--- a/tools/include/uapi/linux/if_link.h
+++ b/tools/include/uapi/linux/if_link.h
@@ -230,6 +230,7 @@  enum {
 	IFLA_INET6_ICMP6STATS,	/* statistics (icmpv6)		*/
 	IFLA_INET6_TOKEN,	/* device token			*/
 	IFLA_INET6_ADDR_GEN_MODE, /* implicit address generator mode */
+	IFLA_INET6_RA_MTU,	/* mtu carried in the RA message */
 	__IFLA_INET6_MAX
 };