ip_gre: add support for i/o_flags update

Now ip_gre is using ip_tunnel_changelink to update it's properties, but ip_tunnel_changelink in ip_tunnel doesn't update i/o_flags as a common function.

o_flags updates would cause that tunnel->tun_hlen / hlen and dev->mtu / needed_headroom need to be recalculated, and dev->(hw_)features need to be updated as well.

Therefore, we can't just add the update into ip_tunnel_update called in ip_tunnel_changelink, and it's also better not to touch ip_tunnel codes.

This patch updates i/o_flags and calls ipgre_link_update to recalculate these gre properties after ip_tunnel_changelink does the common update.

Note that since ipgre_link_update doesn't know the lower dev, it will update gre->hlen, dev->mtu and dev->needed_headroom with the value of 'new tun_hlen - old tun_hlen'. In this way, we can avoid many redundant codes, unlike ip6_gre.

Reported-by Jianlin Shi <[email protected]>

Signed-off-by Xin Long <[email protected]>

---
 net/ipv4/ip_gre.c | 39 +++++++++++++++++++++++++++++++++++++--
 1 file changed, 37 insertions(+), 2 deletions(-)

net/ipv4/ip_gre.c +25 -2

index c105a31..81e1e20 100644
@@ -773,6 +773,30 @@ static netdev_tx_t gre_tap_xmit(struct sk_buff *skb,
        return NETDEV_TX_OK;
 }
 
+static void ipgre_link_update(struct net_device *dev, bool set_mtu)
+{
+       struct ip_tunnel *tunnel = netdev_priv(dev);
+       int len;
+
+       len = tunnel->tun_hlen;
+       tunnel->tun_hlen = gre_calc_hlen(tunnel->parms.o_flags);
+       len = tunnel->tun_hlen - len;
+       tunnel->hlen = tunnel->hlen + len;
+
+       dev->needed_headroom = dev->needed_headroom + len;
+       if (set_mtu)
+               dev->mtu = max_t(int, dev->mtu - len, 68);
+
+       if (!(tunnel->parms.o_flags & TUNNEL_SEQ)) {
+               if (!(tunnel->parms.o_flags & TUNNEL_CSUM) ||
+                   tunnel->encap.type == TUNNEL_ENCAP_NONE) {
+                       dev->features |= NETIF_F_GSO_SOFTWARE;
+                       dev->hw_features |= NETIF_F_GSO_SOFTWARE;
+               }
+               dev->features |= NETIF_F_LLTX;
+       }
+}
+
 static int ipgre_tunnel_ioctl(struct net_device *dev,
                              struct ifreq *ifr, int cmd)
 {

@@ -1307,9 +1331,9 @@ static int ipgre_changelink(struct net_device *dev, struct nlattr *tb[],
                            struct netlink_ext_ack *extack)
 {
        struct ip_tunnel *t = netdev_priv(dev);
-       struct ip_tunnel_parm p;
        struct ip_tunnel_encap ipencap;
        __u32 fwmark = t->fwmark;
+       struct ip_tunnel_parm p;
        int err;
 
        if (ipgre_netlink_encap_parms(data, &ipencap)) {

@@ -1322,7 +1346,18 @@ static int ipgre_changelink(struct net_device *dev, struct nlattr *tb[],
        err = ipgre_netlink_parms(dev, data, tb, &p, &fwmark);
        if (err < 0)
                return err;
-       return ip_tunnel_changelink(dev, tb, &p, fwmark);

As patch 'ip_gre: add the support for i/o_flags update via netlink' did for netlink, we also need to do the same job for these update via ioctl.

This patch is to update i/o_flags and call ipgre_link_update to recalculate these gre properties after ip_tunnel_ioctl does the common update.

Signed-off-by Xin Long <[email protected]>

---

ip_gre is using as many ip_tunnel apis as possible, newlink works fine as gre would do it's own part in .ndo_init. But when changing link, ip_tunnel_changelink doesn't even update i/o_flags, and also the update of these flags would cause some other gre's properties need to be updated or recalculated.

These two patch are to add i/o_flags update and then do adjustment on some gre's properties according to the new i/o_flags.