From c6741fbed6dc0f183d26c4b6bca4517672f92e6c Mon Sep 17 00:00:00 2001 From: Stefano Brivio Date: Thu, 15 Mar 2018 17:17:11 +0100 Subject: vti6: Properly adjust vti6 MTU from MTU of lower device If a lower device is found, we don't need to subtract LL_MAX_HEADER to calculate our MTU: just use its MTU, the link layer headers are already taken into account by it. If the lower device is not found, start from ETH_DATA_LEN instead, and only in this case subtract a worst-case LL_MAX_HEADER. We then need to subtract our additional IPv6 header from the calculation. While at it, note that vti6 doesn't have a hardware header, so it doesn't need to set dev->hard_header_len. And as vti6_link_config() now always sets the MTU, there's no need to set a default value in vti6_dev_setup(). This makes the behaviour consistent with IPv4 vti, after commit a32452366b72 ("vti4: Don't count header length twice."), which was accidentally reverted by merge commit f895f0cfbb77 ("Merge branch 'master' of git://git.kernel.org/pub/scm/linux/kernel/git/klassert/ipsec"). While commit 53c81e95df17 ("ip6_vti: adjust vti mtu according to mtu of lower device") improved on the original situation, this was still not ideal. As reported in that commit message itself, if we start from an underlying veth MTU of 9000, we end up with an MTU of 8832, that is, 9000 - LL_MAX_HEADER - sizeof(ipv6hdr). This should simply be 8880, or 9000 - sizeof(ipv6hdr) instead: we found the lower device (veth) and we know we don't have any additional link layer header, so there's no need to subtract an hypothetical worst-case number. Fixes: 53c81e95df17 ("ip6_vti: adjust vti mtu according to mtu of lower device") Signed-off-by: Stefano Brivio Acked-by: Sabrina Dubroca Signed-off-by: Steffen Klassert --- net/ipv6/ip6_vti.c | 10 ++++++---- 1 file changed, 6 insertions(+), 4 deletions(-) (limited to 'net/ipv6/ip6_vti.c') diff --git a/net/ipv6/ip6_vti.c b/net/ipv6/ip6_vti.c index fa3ae1cb50d3..2ceef41cc097 100644 --- a/net/ipv6/ip6_vti.c +++ b/net/ipv6/ip6_vti.c @@ -627,6 +627,7 @@ static void vti6_link_config(struct ip6_tnl *t) struct net_device *dev = t->dev; struct __ip6_tnl_parm *p = &t->parms; struct net_device *tdev = NULL; + int mtu; memcpy(dev->dev_addr, &p->laddr, sizeof(struct in6_addr)); memcpy(dev->broadcast, &p->raddr, sizeof(struct in6_addr)); @@ -656,8 +657,11 @@ static void vti6_link_config(struct ip6_tnl *t) tdev = __dev_get_by_index(t->net, p->link); if (tdev) - dev->mtu = max_t(int, tdev->mtu - dev->hard_header_len, - IPV6_MIN_MTU); + mtu = tdev->mtu - sizeof(struct ipv6hdr); + else + mtu = ETH_DATA_LEN - LL_MAX_HEADER - sizeof(struct ipv6hdr); + + dev->mtu = max_t(int, mtu, IPV6_MIN_MTU); } /** @@ -866,8 +870,6 @@ static void vti6_dev_setup(struct net_device *dev) dev->priv_destructor = vti6_dev_free; dev->type = ARPHRD_TUNNEL6; - dev->hard_header_len = LL_MAX_HEADER + sizeof(struct ipv6hdr); - dev->mtu = ETH_DATA_LEN; dev->min_mtu = IPV6_MIN_MTU; dev->max_mtu = IP_MAX_MTU; dev->flags |= IFF_NOARP; -- cgit From 7a67e69a339a6824be2fc483073782ab2f47fcd2 Mon Sep 17 00:00:00 2001 From: Stefano Brivio Date: Thu, 15 Mar 2018 17:17:12 +0100 Subject: vti6: Keep set MTU on link creation or change, validate it In vti6_link_config(), if MTU is already given on link creation or change, validate and use it instead of recomputing it. To do that, we need to propagate the knowledge that MTU was set by userspace all the way down to vti6_link_config(). To keep this simple, vti6_dev_init() sets the new 'keep_mtu' argument of vti6_link_config() to true: on initialization, we don't have convenient access to netlink attributes there, but we will anyway check whether dev->mtu is set in vti6_link_config(). If it's non-zero, it was set to the value of the IFLA_MTU attribute during creation. Otherwise, determine a reasonable value. Fixes: ed1efb2aefbb ("ipv6: Add support for IPsec virtual tunnel interfaces") Fixes: 53c81e95df17 ("ip6_vti: adjust vti mtu according to mtu of lower device") Signed-off-by: Stefano Brivio Acked-by: Sabrina Dubroca Signed-off-by: Steffen Klassert --- net/ipv6/ip6_vti.c | 24 ++++++++++++++++-------- 1 file changed, 16 insertions(+), 8 deletions(-) (limited to 'net/ipv6/ip6_vti.c') diff --git a/net/ipv6/ip6_vti.c b/net/ipv6/ip6_vti.c index 2ceef41cc097..971175142e14 100644 --- a/net/ipv6/ip6_vti.c +++ b/net/ipv6/ip6_vti.c @@ -622,7 +622,7 @@ static int vti6_err(struct sk_buff *skb, struct inet6_skb_parm *opt, return 0; } -static void vti6_link_config(struct ip6_tnl *t) +static void vti6_link_config(struct ip6_tnl *t, bool keep_mtu) { struct net_device *dev = t->dev; struct __ip6_tnl_parm *p = &t->parms; @@ -641,6 +641,11 @@ static void vti6_link_config(struct ip6_tnl *t) else dev->flags &= ~IFF_POINTOPOINT; + if (keep_mtu && dev->mtu) { + dev->mtu = clamp(dev->mtu, dev->min_mtu, dev->max_mtu); + return; + } + if (p->flags & IP6_TNL_F_CAP_XMIT) { int strict = (ipv6_addr_type(&p->raddr) & (IPV6_ADDR_MULTICAST | IPV6_ADDR_LINKLOCAL)); @@ -668,12 +673,14 @@ static void vti6_link_config(struct ip6_tnl *t) * vti6_tnl_change - update the tunnel parameters * @t: tunnel to be changed * @p: tunnel configuration parameters + * @keep_mtu: MTU was set from userspace, don't re-compute it * * Description: * vti6_tnl_change() updates the tunnel parameters **/ static int -vti6_tnl_change(struct ip6_tnl *t, const struct __ip6_tnl_parm *p) +vti6_tnl_change(struct ip6_tnl *t, const struct __ip6_tnl_parm *p, + bool keep_mtu) { t->parms.laddr = p->laddr; t->parms.raddr = p->raddr; @@ -683,11 +690,12 @@ vti6_tnl_change(struct ip6_tnl *t, const struct __ip6_tnl_parm *p) t->parms.proto = p->proto; t->parms.fwmark = p->fwmark; dst_cache_reset(&t->dst_cache); - vti6_link_config(t); + vti6_link_config(t, keep_mtu); return 0; } -static int vti6_update(struct ip6_tnl *t, struct __ip6_tnl_parm *p) +static int vti6_update(struct ip6_tnl *t, struct __ip6_tnl_parm *p, + bool keep_mtu) { struct net *net = dev_net(t->dev); struct vti6_net *ip6n = net_generic(net, vti6_net_id); @@ -695,7 +703,7 @@ static int vti6_update(struct ip6_tnl *t, struct __ip6_tnl_parm *p) vti6_tnl_unlink(ip6n, t); synchronize_net(); - err = vti6_tnl_change(t, p); + err = vti6_tnl_change(t, p, keep_mtu); vti6_tnl_link(ip6n, t); netdev_state_change(t->dev); return err; @@ -808,7 +816,7 @@ vti6_ioctl(struct net_device *dev, struct ifreq *ifr, int cmd) } else t = netdev_priv(dev); - err = vti6_update(t, &p1); + err = vti6_update(t, &p1, false); } if (t) { err = 0; @@ -907,7 +915,7 @@ static int vti6_dev_init(struct net_device *dev) if (err) return err; - vti6_link_config(t); + vti6_link_config(t, true); return 0; } @@ -1012,7 +1020,7 @@ static int vti6_changelink(struct net_device *dev, struct nlattr *tb[], } else t = netdev_priv(dev); - return vti6_update(t, &p); + return vti6_update(t, &p, tb && tb[IFLA_MTU]); } static size_t vti6_get_size(const struct net_device *dev) -- cgit From f8a554b4aa9686bb2c12f6bae516e58783289a03 Mon Sep 17 00:00:00 2001 From: Stefano Brivio Date: Thu, 15 Mar 2018 17:17:13 +0100 Subject: vti6: Fix dev->max_mtu setting We shouldn't allow a tunnel to have IP_MAX_MTU as MTU, because another IPv6 header is going on top of our packets. Without this patch, we might end up building packets bigger than IP_MAX_MTU. Fixes: b96f9afee4eb ("ipv4/6: use core net MTU range checking") Signed-off-by: Stefano Brivio Acked-by: Sabrina Dubroca Signed-off-by: Steffen Klassert --- net/ipv6/ip6_vti.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'net/ipv6/ip6_vti.c') diff --git a/net/ipv6/ip6_vti.c b/net/ipv6/ip6_vti.c index 971175142e14..ce18cd20389d 100644 --- a/net/ipv6/ip6_vti.c +++ b/net/ipv6/ip6_vti.c @@ -879,7 +879,7 @@ static void vti6_dev_setup(struct net_device *dev) dev->type = ARPHRD_TUNNEL6; dev->min_mtu = IPV6_MIN_MTU; - dev->max_mtu = IP_MAX_MTU; + dev->max_mtu = IP_MAX_MTU - sizeof(struct ipv6hdr); dev->flags |= IFF_NOARP; dev->addr_len = sizeof(struct in6_addr); netif_keep_dst(dev); -- cgit