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Date: Tue, 6 Oct 2015 11:26:31 -0700
From: Pravin Shelar <pshelar@...ira.com>
To: Jiri Benc <jbenc@...hat.com>
Cc: netdev <netdev@...r.kernel.org>
Subject: Re: [PATCH net] openvswitch: Fix egress tunnel info.
On Tue, Oct 6, 2015 at 8:42 AM, Jiri Benc <jbenc@...hat.com> wrote:
> Some more feedback after doing a deeper review.
>
Thanks for the review.
> On Mon, 5 Oct 2015 10:58:17 -0700, Pravin B Shelar wrote:
>> --- a/drivers/net/geneve.c
>> +++ b/drivers/net/geneve.c
>> @@ -703,6 +703,32 @@ err:
>> return NETDEV_TX_OK;
>> }
>>
>> +static int geneve_egress_tun_info(struct net_device *dev, struct sk_buff *skb,
>> + struct ip_tunnel_info *egress_tun_info,
>> + const void **egress_tun_opts)
>> +{
>> + struct geneve_dev *geneve = netdev_priv(dev);
>> + struct ip_tunnel_info *info;
>> + struct rtable *rt;
>> + struct flowi4 fl4;
>> + __be16 sport;
>> +
>> + info = skb_tunnel_info(skb);
>> + if (ip_tunnel_info_af(info) != AF_INET)
>> + return -EINVAL;
>> +
>> + rt = geneve_get_rt(skb, dev, &fl4, info);
>
> This will increase dev tx error stats in case the lookup fails which is
> probably something we don't want.
>
right, I will fix it.
> [...]
>> --- a/include/linux/netdevice.h
>> +++ b/include/linux/netdevice.h
>> @@ -60,6 +60,7 @@ struct wireless_dev;
>> /* 802.15.4 specific */
>> struct wpan_dev;
>> struct mpls_dev;
>> +struct ip_tunnel_info;
>>
>> void netdev_set_default_ethtool_ops(struct net_device *dev,
>> const struct ethtool_ops *ops);
>> @@ -1054,6 +1055,11 @@ typedef u16 (*select_queue_fallback_t)(struct net_device *dev,
>> * This function is used to pass protocol port error state information
>> * to the switch driver. The switch driver can react to the proto_down
>> * by doing a phys down on the associated switch port.
>> + * int (*ndo_get_egress_info)(struct net_device *dev, struct sk_buff *skb,
>> + * __be32 *saddr, __be16 *sport, __be16 *dport);
>> + * This function is used to get egress tunnel information for given skb.
>> + * This is useful for retrieving outer tunnel header parameters while
>> + * sampling packet.
>> *
>> */
>> struct net_device_ops {
>> @@ -1227,6 +1233,10 @@ struct net_device_ops {
>> int (*ndo_get_iflink)(const struct net_device *dev);
>> int (*ndo_change_proto_down)(struct net_device *dev,
>> bool proto_down);
>> + int (*ndo_get_egress_info)(struct net_device *dev,
>> + struct sk_buff *skb,
>> + struct ip_tunnel_info *egress_tun_info,
>> + const void **egress_tun_opts);
>
> This should have at least a better name to reflect it is about IP
> tunnels.
>
> But I don't like having an IP tunnel specific ndo, that doesn't sound
> right. The real thing that is wanted here is to complete the dst
> metadata. What about:
>
> int (*ndo_fill_metadata_dst)(struct net_device *dev, struct sk_buff *skb);
>
This is nicer, I will change it.
> The function will use skb_tunnel_info to get the template info, then
> skb_dst_drop and allocate and attach a fully populated metadata_dst.
> The egress_tun_info in struct dp_upcall_info then can be completely
> dropped, as all the necessary tunnel information will be available
> through skb_tunnel_info(skb). Also, when implemented correctly, such
> skb will be just sent out without route lookups etc. if afterwards
> handed to ndo_start_xmit.
>
I do not see need to drop and reallocate dst in this operation. I just
need to set source IP address and source and dst port in the metadata
dst already set in skb.
This fill_metadata function is not called for every packet so
ndo_start_xmit() still needs to do route lookup.
egress_tun_info in dp_upcall_info is required to check for failure. It
would be only set on successful fill_metadata operation.
> [...]
>> --- a/include/net/ip_tunnels.h
>> +++ b/include/net/ip_tunnels.h
>> @@ -337,6 +337,11 @@ void __init ip_tunnel_core_init(void);
>> void ip_tunnel_need_metadata(void);
>> void ip_tunnel_unneed_metadata(void);
>>
>> +void ipv4_egress_info_init(struct ip_tunnel_info *egress_tun_info,
>> + const void **egress_tun_opts,
>> + struct ip_tunnel_info *info, __be32 saddr,
>> + __be16 sport, __be16 dport);
>
> Please use the ip_tunnel prefix as the rest of the functions, this is
> not ipv4 egress info but ip *tunnel* egress info.
>
> Also, it's not clear what the difference between "egress_tun_info" and
> "info" is. I'd suggest to use "dst_info" and "src_info" or something
> similar.
>
src and dst prefix is confusing here, since it is nothing to do tunnel
endpoints. Anyways its moot point after changes above there is no need
to have these functions.
> [...]
>> --- a/net/ipv4/ip_tunnel_core.c
>> +++ b/net/ipv4/ip_tunnel_core.c
>> @@ -424,3 +424,40 @@ void ip_tunnel_unneed_metadata(void)
>> static_key_slow_dec(&ip_tunnel_metadata_cnt);
>> }
>> EXPORT_SYMBOL_GPL(ip_tunnel_unneed_metadata);
>> +
>> +static void tnl_egress_opts_init(struct ip_tunnel_info *egress_tun_info,
>> + const void **egress_tun_opts,
>> + struct ip_tunnel_info *info)
>> +{
>> + egress_tun_info->options_len = info->options_len;
>> + egress_tun_info->mode = info->mode;
>> +
>> + /* Tunnel options. */
>> + if (info->options_len)
>> + *egress_tun_opts = ip_tunnel_info_opts(info);
>> + else
>> + *egress_tun_opts = NULL;
>> +}
>> +
>> +void ipv4_egress_info_init(struct ip_tunnel_info *egress_tun_info,
>> + const void **egress_tun_opts,
>> + struct ip_tunnel_info *info, __be32 saddr,
>> + __be16 sport, __be16 dport)
>> +{
>> + const struct ip_tunnel_key *tun_key;
>> +
>> + /* Generate egress_tun_info based on tun_info,
>> + * saddr, tp_src and tp_dst
>> + */
>> + tun_key = &egress_tun_info->key;
>> + ip_tunnel_key_init(&egress_tun_info->key,
>
> Just pass tun_key as the first parameter, it will be clearer what's
> going on. (I believe the assignments that have no effect will be
> optimized out by the compiler, since ip_tunnel_key_init is an inline
> function.)
>
Same as above.
>> + saddr, tun_key->u.ipv4.dst,
>> + tun_key->tos,
>> + tun_key->ttl,
>> + sport, dport,
>> + tun_key->tun_id,
>> + tun_key->tun_flags);
>
> --
> Jiri Benc
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