This patch adds changelink rtnl operation support for geneve devices.
Code changes involve:
  - refactor geneve_newlink into geneve_nl2info to be used by both
    geneve_newlink and geneve_changelink
  - geneve_nl2info takes a changelink boolean argument to isolate
    changelink checks and updates.
  - Allow changing only a few attributes:
    - return -EOPNOTSUPP for attributes that cannot be changed for
      now. Incremental patches can make the non-supported one
      available in the future if needed.

Signed-off-by: Girish Moodalbail <girish.moodalb...@oracle.com>
---
 drivers/net/geneve.c | 149 ++++++++++++++++++++++++++++++++++++++++-----------
 1 file changed, 117 insertions(+), 32 deletions(-)

diff --git a/drivers/net/geneve.c b/drivers/net/geneve.c
index dec5d56..6528910 100644
--- a/drivers/net/geneve.c
+++ b/drivers/net/geneve.c
@@ -1112,6 +1112,18 @@ static bool is_tnl_info_zero(const struct ip_tunnel_info 
*info)
                return true;
 }
 
+static inline bool geneve_dst_addr_equal(struct ip_tunnel_info *a,
+                                        struct ip_tunnel_info *b)
+{
+       if (ip_tunnel_info_af(a) != ip_tunnel_info_af(b))
+               return false;
+
+       if (ip_tunnel_info_af(a) == AF_INET)
+               return a->key.u.ipv4.dst == b->key.u.ipv4.dst;
+       else
+               return ipv6_addr_equal(&a->key.u.ipv6.dst, &b->key.u.ipv6.dst);
+}
+
 static int geneve_configure(struct net *net, struct net_device *dev,
                            const struct ip_tunnel_info *info,
                            bool metadata, bool ipv6_rx_csum)
@@ -1169,45 +1181,58 @@ static void init_tnl_info(struct ip_tunnel_info *info, 
__u16 dst_port)
        info->key.tp_dst = htons(dst_port);
 }
 
-static int geneve_newlink(struct net *net, struct net_device *dev,
-                         struct nlattr *tb[], struct nlattr *data[])
+static int geneve_nl2info(struct net_device *dev, struct nlattr *tb[],
+                         struct nlattr *data[], struct ip_tunnel_info *info,
+                         bool *metadata, bool *use_udp6_rx_checksums,
+                         bool changelink)
 {
-       bool use_udp6_rx_checksums = false;
-       struct ip_tunnel_info info;
-       bool metadata = false;
+       struct geneve_dev *geneve = netdev_priv(dev);
 
-       init_tnl_info(&info, GENEVE_UDP_PORT);
+       if (changelink) {
+               /* if changelink operation, start with old existing info */
+               memcpy(info, &geneve->info, sizeof(*info));
+               *metadata = geneve->collect_md;
+               *use_udp6_rx_checksums = geneve->use_udp6_rx_checksums;
+       } else {
+               init_tnl_info(info, GENEVE_UDP_PORT);
+       }
 
        if (data[IFLA_GENEVE_REMOTE] && data[IFLA_GENEVE_REMOTE6])
                return -EINVAL;
 
        if (data[IFLA_GENEVE_REMOTE]) {
-               info.key.u.ipv4.dst =
+               info->key.u.ipv4.dst =
                        nla_get_in_addr(data[IFLA_GENEVE_REMOTE]);
 
-               if (IN_MULTICAST(ntohl(info.key.u.ipv4.dst))) {
+               if (IN_MULTICAST(ntohl(info->key.u.ipv4.dst))) {
                        netdev_dbg(dev, "multicast remote is unsupported\n");
                        return -EINVAL;
                }
+               if (changelink &&
+                   ip_tunnel_info_af(&geneve->info) == AF_INET6) {
+                       info->mode &= ~IP_TUNNEL_INFO_IPV6;
+                       info->key.tun_flags &= ~TUNNEL_CSUM;
+                       *use_udp6_rx_checksums = false;
+               }
        }
 
        if (data[IFLA_GENEVE_REMOTE6]) {
  #if IS_ENABLED(CONFIG_IPV6)
-               info.mode = IP_TUNNEL_INFO_IPV6;
-               info.key.u.ipv6.dst =
+               info->mode = IP_TUNNEL_INFO_IPV6;
+               info->key.u.ipv6.dst =
                        nla_get_in6_addr(data[IFLA_GENEVE_REMOTE6]);
 
-               if (ipv6_addr_type(&info.key.u.ipv6.dst) &
+               if (ipv6_addr_type(&info->key.u.ipv6.dst) &
                    IPV6_ADDR_LINKLOCAL) {
                        netdev_dbg(dev, "link-local remote is unsupported\n");
                        return -EINVAL;
                }
-               if (ipv6_addr_is_multicast(&info.key.u.ipv6.dst)) {
+               if (ipv6_addr_is_multicast(&info->key.u.ipv6.dst)) {
                        netdev_dbg(dev, "multicast remote is unsupported\n");
                        return -EINVAL;
                }
-               info.key.tun_flags |= TUNNEL_CSUM;
-               use_udp6_rx_checksums = true;
+               info->key.tun_flags |= TUNNEL_CSUM;
+               *use_udp6_rx_checksums = true;
 #else
                return -EPFNOSUPPORT;
 #endif
@@ -1216,48 +1241,107 @@ static int geneve_newlink(struct net *net, struct 
net_device *dev,
        if (data[IFLA_GENEVE_ID]) {
                __u32 vni;
                __u8 tvni[3];
+               __be64 tunid;
 
                vni = nla_get_u32(data[IFLA_GENEVE_ID]);
                tvni[0] = (vni & 0x00ff0000) >> 16;
                tvni[1] = (vni & 0x0000ff00) >> 8;
                tvni[2] =  vni & 0x000000ff;
 
-               info.key.tun_id = vni_to_tunnel_id(tvni);
+               tunid = vni_to_tunnel_id(tvni);
+               if (changelink && (tunid != info->key.tun_id))
+                       return -EOPNOTSUPP;
+               info->key.tun_id = tunid;
        }
+
        if (data[IFLA_GENEVE_TTL])
-               info.key.ttl = nla_get_u8(data[IFLA_GENEVE_TTL]);
+               info->key.ttl = nla_get_u8(data[IFLA_GENEVE_TTL]);
 
        if (data[IFLA_GENEVE_TOS])
-               info.key.tos = nla_get_u8(data[IFLA_GENEVE_TOS]);
+               info->key.tos = nla_get_u8(data[IFLA_GENEVE_TOS]);
 
        if (data[IFLA_GENEVE_LABEL]) {
-               info.key.label = nla_get_be32(data[IFLA_GENEVE_LABEL]) &
+               info->key.label = nla_get_be32(data[IFLA_GENEVE_LABEL]) &
                                  IPV6_FLOWLABEL_MASK;
-               if (info.key.label && (!(info.mode & IP_TUNNEL_INFO_IPV6)))
+               if (info->key.label && (!(info->mode & IP_TUNNEL_INFO_IPV6)))
                        return -EINVAL;
        }
 
-       if (data[IFLA_GENEVE_PORT])
-               info.key.tp_dst = nla_get_be16(data[IFLA_GENEVE_PORT]);
+       if (data[IFLA_GENEVE_PORT]) {
+               if (changelink)
+                       return -EOPNOTSUPP;
+               info->key.tp_dst = nla_get_be16(data[IFLA_GENEVE_PORT]);
+       }
+
+       if (data[IFLA_GENEVE_COLLECT_METADATA]) {
+               if (changelink)
+                       return -EOPNOTSUPP;
+               *metadata = true;
+       }
+
+       if (data[IFLA_GENEVE_UDP_CSUM]) {
+               if (changelink)
+                       return -EOPNOTSUPP;
+               if (nla_get_u8(data[IFLA_GENEVE_UDP_CSUM]))
+                       info->key.tun_flags |= TUNNEL_CSUM;
+       }
+
+       if (data[IFLA_GENEVE_UDP_ZERO_CSUM6_TX]) {
+               if (changelink)
+                       return -EOPNOTSUPP;
+               if (nla_get_u8(data[IFLA_GENEVE_UDP_ZERO_CSUM6_TX]))
+                       info->key.tun_flags &= ~TUNNEL_CSUM;
+       }
 
-       if (data[IFLA_GENEVE_COLLECT_METADATA])
-               metadata = true;
+       if (data[IFLA_GENEVE_UDP_ZERO_CSUM6_RX]) {
+               if (changelink)
+                       return -EOPNOTSUPP;
+               if (nla_get_u8(data[IFLA_GENEVE_UDP_ZERO_CSUM6_RX]))
+                       *use_udp6_rx_checksums = false;
+       }
 
-       if (data[IFLA_GENEVE_UDP_CSUM] &&
-           nla_get_u8(data[IFLA_GENEVE_UDP_CSUM]))
-               info.key.tun_flags |= TUNNEL_CSUM;
+       return 0;
+}
 
-       if (data[IFLA_GENEVE_UDP_ZERO_CSUM6_TX] &&
-           nla_get_u8(data[IFLA_GENEVE_UDP_ZERO_CSUM6_TX]))
-               info.key.tun_flags &= ~TUNNEL_CSUM;
+static int geneve_newlink(struct net *net, struct net_device *dev,
+                         struct nlattr *tb[], struct nlattr *data[])
+{
+       bool use_udp6_rx_checksums = false;
+       struct ip_tunnel_info info;
+       bool metadata = false;
+       int err;
 
-       if (data[IFLA_GENEVE_UDP_ZERO_CSUM6_RX] &&
-           nla_get_u8(data[IFLA_GENEVE_UDP_ZERO_CSUM6_RX]))
-               use_udp6_rx_checksums = false;
+       err = geneve_nl2info(dev, tb, data, &info, &metadata,
+                            &use_udp6_rx_checksums, false);
+       if (err)
+               return err;
 
        return geneve_configure(net, dev, &info, metadata, 
use_udp6_rx_checksums);
 }
 
+static int geneve_changelink(struct net_device *dev, struct nlattr *tb[],
+                            struct nlattr *data[])
+{
+       struct geneve_dev *geneve = netdev_priv(dev);
+       struct ip_tunnel_info info;
+       bool metadata = false;
+       bool use_udp6_rx_checksums = false;
+       int err;
+
+       err = geneve_nl2info(dev, tb, data, &info, &metadata,
+                            &use_udp6_rx_checksums, true);
+       if (err)
+               return err;
+
+       if (!geneve_dst_addr_equal(&geneve->info, &info))
+               dst_cache_reset(&info.dst_cache);
+       geneve->info = info;
+       geneve->collect_md = metadata;
+       geneve->use_udp6_rx_checksums = use_udp6_rx_checksums;
+
+       return 0;
+}
+
 static void geneve_dellink(struct net_device *dev, struct list_head *head)
 {
        struct geneve_dev *geneve = netdev_priv(dev);
@@ -1344,6 +1428,7 @@ static int geneve_fill_info(struct sk_buff *skb, const 
struct net_device *dev)
        .setup          = geneve_setup,
        .validate       = geneve_validate,
        .newlink        = geneve_newlink,
+       .changelink     = geneve_changelink,
        .dellink        = geneve_dellink,
        .get_size       = geneve_get_size,
        .fill_info      = geneve_fill_info,
-- 
1.8.3.1

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