| Message ID | 1513691961-19692-1-git-send-email-alexey.kodanev@oracle.com |
|---|---|
| State | Accepted, archived |
| Delegated to: | David Miller |
| Headers | show |
| Series | [net-next,v4] ip6_vti: adjust vti mtu according to mtu of lower device | expand |
From: Alexey Kodanev <alexey.kodanev@oracle.com> Date: Tue, 19 Dec 2017 16:59:21 +0300 > LTP/udp6_ipsec_vti tests fail when sending large UDP datagrams over > ip6_vti that require fragmentation and the underlying device has an > MTU smaller than 1500 plus some extra space for headers. This happens > because ip6_vti, by default, sets MTU to ETH_DATA_LEN and not updating > it depending on a destination address or link parameter. Further > attempts to send UDP packets may succeed because pmtu gets updated on > ICMPV6_PKT_TOOBIG in vti6_err(). > > In case the lower device has larger MTU size, e.g. 9000, ip6_vti works > but not using the possible maximum size, output packets have 1500 limit. > > The above cases require manual MTU setup after ip6_vti creation. However > ip_vti already updates MTU based on lower device with ip_tunnel_bind_dev(). > > Here is the example when the lower device MTU is set to 9000: ... > Reported-by: Petr Vorel <pvorel@suse.cz> > Signed-off-by: Alexey Kodanev <alexey.kodanev@oracle.com> Applied, thanks Alexey.
diff --git a/net/ipv6/ip6_vti.c b/net/ipv6/ip6_vti.c index dbb74f3..18caa95 100644 --- a/net/ipv6/ip6_vti.c +++ b/net/ipv6/ip6_vti.c @@ -626,6 +626,7 @@ 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; memcpy(dev->dev_addr, &p->laddr, sizeof(struct in6_addr)); memcpy(dev->broadcast, &p->raddr, sizeof(struct in6_addr)); @@ -638,6 +639,25 @@ static void vti6_link_config(struct ip6_tnl *t) dev->flags |= IFF_POINTOPOINT; else dev->flags &= ~IFF_POINTOPOINT; + + if (p->flags & IP6_TNL_F_CAP_XMIT) { + int strict = (ipv6_addr_type(&p->raddr) & + (IPV6_ADDR_MULTICAST | IPV6_ADDR_LINKLOCAL)); + struct rt6_info *rt = rt6_lookup(t->net, + &p->raddr, &p->laddr, + p->link, strict); + + if (rt) + tdev = rt->dst.dev; + ip6_rt_put(rt); + } + + if (!tdev && p->link) + 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); } /**
LTP/udp6_ipsec_vti tests fail when sending large UDP datagrams over ip6_vti that require fragmentation and the underlying device has an MTU smaller than 1500 plus some extra space for headers. This happens because ip6_vti, by default, sets MTU to ETH_DATA_LEN and not updating it depending on a destination address or link parameter. Further attempts to send UDP packets may succeed because pmtu gets updated on ICMPV6_PKT_TOOBIG in vti6_err(). In case the lower device has larger MTU size, e.g. 9000, ip6_vti works but not using the possible maximum size, output packets have 1500 limit. The above cases require manual MTU setup after ip6_vti creation. However ip_vti already updates MTU based on lower device with ip_tunnel_bind_dev(). Here is the example when the lower device MTU is set to 9000: # ip a sh ltp_ns_veth2 ltp_ns_veth2@if7: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 9000 ... inet 10.0.0.2/24 scope global ltp_ns_veth2 inet6 fd00::2/64 scope global # ip li add vti6 type vti6 local fd00::2 remote fd00::1 # ip li show vti6 vti6@NONE: <POINTOPOINT,NOARP> mtu 1500 ... link/tunnel6 fd00::2 peer fd00::1 After the patch: # ip li add vti6 type vti6 local fd00::2 remote fd00::1 # ip li show vti6 vti6@NONE: <POINTOPOINT,NOARP> mtu 8832 ... link/tunnel6 fd00::2 peer fd00::1 Reported-by: Petr Vorel <pvorel@suse.cz> Signed-off-by: Alexey Kodanev <alexey.kodanev@oracle.com> --- v4: * remove an empty line between variable declarations * update the commit message to reflect unexpected behavior with an MTU larger than 1500. v3: * fix style issue with curly braces around single-statement if block v2: * cleanup commit message issues (thanks to Shannon) * handle the case when we don't have route but have device parameter * cast new MTU to int and then check the maximum (tdev->mtu can be less than dev->hard_header_len) net/ipv6/ip6_vti.c | 20 ++++++++++++++++++++ 1 files changed, 20 insertions(+), 0 deletions(-)