This is possible via the ioctl API: > ip -6 tunnel change ip6tnl0 mode any Let's align the netlink API: > ip link set ip6tnl0 type ip6tnl mode any Signed-off-by: Nicolas Dichtel --- v2 -> v3: - reformat the comment in ip6_tnl0_update() - don't redeclare the variable 't' in ip6_tnl_changelink() v1 -> v2: - returns an error if the user attempts to change anything other than the proto net/ipv6/ip6_tunnel.c | 41 ++++++++++++++++++++++++++++++++++++----- 1 file changed, 36 insertions(+), 5 deletions(-) diff --git a/net/ipv6/ip6_tunnel.c b/net/ipv6/ip6_tunnel.c index a885bb5c98ea..436e077061d1 100644 --- a/net/ipv6/ip6_tunnel.c +++ b/net/ipv6/ip6_tunnel.c @@ -1562,11 +1562,22 @@ static void ip6_tnl_update(struct ip6_tnl *t, struct __ip6_tnl_parm *p) netdev_state_change(t->dev); } -static void ip6_tnl0_update(struct ip6_tnl *t, struct __ip6_tnl_parm *p) +static int ip6_tnl0_update(struct ip6_tnl *t, struct __ip6_tnl_parm *p, + bool strict) { - /* for default tnl0 device allow to change only the proto */ + /* For the default ip6tnl0 device, allow changing only the protocol + * (the IP6_TNL_F_CAP_PER_PACKET flag is set on ip6tnl0, and all other + * parameters are 0). + */ + if (strict && + (!ipv6_addr_any(&p->laddr) || !ipv6_addr_any(&p->raddr) || + p->flags != t->parms.flags || p->hop_limit || p->encap_limit || + p->flowinfo || p->link || p->fwmark || p->collect_md)) + return -EINVAL; + t->parms.proto = p->proto; netdev_state_change(t->dev); + return 0; } static void @@ -1680,7 +1691,7 @@ ip6_tnl_siocdevprivate(struct net_device *dev, struct ifreq *ifr, } else t = netdev_priv(dev); if (dev == ip6n->fb_tnl_dev) - ip6_tnl0_update(t, &p1); + ip6_tnl0_update(t, &p1, false); else ip6_tnl_update(t, &p1); } @@ -2053,8 +2064,28 @@ static int ip6_tnl_changelink(struct net_device *dev, struct nlattr *tb[], struct ip6_tnl_net *ip6n = net_generic(net, ip6_tnl_net_id); struct ip_tunnel_encap ipencap; - if (dev == ip6n->fb_tnl_dev) - return -EINVAL; + if (dev == ip6n->fb_tnl_dev) { + if (ip_tunnel_netlink_encap_parms(data, &ipencap)) { + /* iproute2 always sets TUNNEL_ENCAP_FLAG_CSUM6, so + * let's ignore this flag. + */ + ipencap.flags &= ~TUNNEL_ENCAP_FLAG_CSUM6; + if (memchr_inv(&ipencap, 0, sizeof(ipencap))) { + NL_SET_ERR_MSG(extack, + "Only protocol can be changed for fallback tunnel, not encap params"); + return -EINVAL; + } + } + + ip6_tnl_netlink_parms(data, &p); + if (ip6_tnl0_update(t, &p, true) < 0) { + NL_SET_ERR_MSG(extack, + "Only protocol can be changed for fallback tunnel"); + return -EINVAL; + } + + return 0; + } if (ip_tunnel_netlink_encap_parms(data, &ipencap)) { int err = ip6_tnl_encap_setup(t, &ipencap); -- 2.47.1