Re: [PATCH RFC v1 net-next 06/12] net: core: dev: Add dev_fill_bridge_path()

[Eric Woudstra]

On 10/14/24 8:59 AM, Nikolay Aleksandrov wrote:
> On 13/10/2024 21:55, Eric Woudstra wrote:
>> New function dev_fill_bridge_path(), similar to dev_fill_forward_path().
>> It handles starting from a bridge port instead of the bridge master.
>> The structures ctx and nft_forward_info need to be already filled in with
>> the (vlan) encaps.
>>
>> Signed-off-by: Eric Woudstra <ericwouds@xxxxxxxxx>
>> ---
>>  include/linux/netdevice.h |  2 +
>>  net/core/dev.c            | 77 ++++++++++++++++++++++++++++++++-------
>>  2 files changed, 66 insertions(+), 13 deletions(-)
>>
>> diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
>> index e87b5e488325..9d80f650345e 100644
>> --- a/include/linux/netdevice.h
>> +++ b/include/linux/netdevice.h
>> @@ -3069,6 +3069,8 @@ void dev_remove_offload(struct packet_offload *po);
>>  
>>  int dev_get_iflink(const struct net_device *dev);
>>  int dev_fill_metadata_dst(struct net_device *dev, struct sk_buff *skb);
>> +int dev_fill_bridge_path(struct net_device_path_ctx *ctx,
>> +			 struct net_device_path_stack *stack);
>>  int dev_fill_forward_path(const struct net_device *dev, const u8 *daddr,
>>  			  struct net_device_path_stack *stack);
>>  struct net_device *__dev_get_by_flags(struct net *net, unsigned short flags,
>> diff --git a/net/core/dev.c b/net/core/dev.c
>> index cd479f5f22f6..49959c4904fc 100644
>> --- a/net/core/dev.c
>> +++ b/net/core/dev.c
>> @@ -713,44 +713,95 @@ static struct net_device_path *dev_fwd_path(struct net_device_path_stack *stack)
>>  	return &stack->path[k];
>>  }
>>  
>> -int dev_fill_forward_path(const struct net_device *dev, const u8 *daddr,
>> -			  struct net_device_path_stack *stack)
>> +static int dev_fill_forward_path_common(struct net_device_path_ctx *ctx,
>> +					struct net_device_path_stack *stack)
>>  {
>>  	const struct net_device *last_dev;
>> -	struct net_device_path_ctx ctx = {
>> -		.dev	= dev,
>> -	};
>>  	struct net_device_path *path;
>>  	int ret = 0;
>>  
>> -	memcpy(ctx.daddr, daddr, sizeof(ctx.daddr));
>> -	stack->num_paths = 0;
>> -	while (ctx.dev && ctx.dev->netdev_ops->ndo_fill_forward_path) {
>> -		last_dev = ctx.dev;
>> +	while (ctx->dev && ctx->dev->netdev_ops->ndo_fill_forward_path) {
>> +		last_dev = ctx->dev;
>>  		path = dev_fwd_path(stack);
>>  		if (!path)
>>  			return -1;
>>  
>>  		memset(path, 0, sizeof(struct net_device_path));
>> -		ret = ctx.dev->netdev_ops->ndo_fill_forward_path(&ctx, path);
>> +		ret = ctx->dev->netdev_ops->ndo_fill_forward_path(ctx, path);
>>  		if (ret < 0)
>>  			return -1;
>>  
>> -		if (WARN_ON_ONCE(last_dev == ctx.dev))
>> +		if (WARN_ON_ONCE(last_dev == ctx->dev))
>>  			return -1;
>>  	}
>>  
>> -	if (!ctx.dev)
>> +	if (!ctx->dev)
>>  		return ret;
>>  
>>  	path = dev_fwd_path(stack);
>>  	if (!path)
>>  		return -1;
>>  	path->type = DEV_PATH_ETHERNET;
>> -	path->dev = ctx.dev;
>> +	path->dev = ctx->dev;
>> +
>> +	return ret;
>> +}
>> +
>> +int dev_fill_bridge_path(struct net_device_path_ctx *ctx,
>> +			 struct net_device_path_stack *stack)
>> +{
>> +	const struct net_device *last_dev, *br_dev;
>> +	struct net_device_path *path;
>> +	int ret = 0;
>> +
>> +	stack->num_paths = 0;
>> +
>> +	if (!ctx->dev || !netif_is_bridge_port(ctx->dev))
>> +		return -1;
>> +
>> +	br_dev = netdev_master_upper_dev_get_rcu((struct net_device *)ctx->dev);
>> +	if (!br_dev || !br_dev->netdev_ops->ndo_fill_forward_path)
>> +		return -1;
>> +
>> +	last_dev = ctx->dev;
>> +	path = dev_fwd_path(stack);
>> +	if (!path)
>> +		return -1;
>> +
>> +	memset(path, 0, sizeof(struct net_device_path));
>> +	ret = br_dev->netdev_ops->ndo_fill_forward_path(ctx, path);
>> +	if (ret < 0)
>> +		return -1;
>> +
>> +	if (!ctx->dev || WARN_ON_ONCE(last_dev == ctx->dev))
>> +		return -1;
>> +
>> +	if (!netif_is_bridge_master(ctx->dev))
> 
> hmm, do we expect ctx->dev to be a bridge master? Looking at
> br_fill_forward_path, it seems to be == fdb->dst->dev which
> should be the target port

It would indeed be very unlikely. It was a left-over from code I wrote,
thinking that here I could handle cascaded bridges (via vlan-device). I
dropped that, since conntrack does not follow this flow.

So would it be better to only make sure that ctx->dev is not a bridge
master?

	if (netif_is_bridge_master(ctx->dev))
		return -1;

	return dev_fill_forward_path_common(ctx, stack);

>> +		return dev_fill_forward_path_common(ctx, stack);
>> +
>> +	path = dev_fwd_path(stack);
>> +	if (!path)
>> +		return -1;
>> +	path->type = DEV_PATH_ETHERNET;
>> +	path->dev = ctx->dev;
>>  
>>  	return ret;
>>  }
>> +EXPORT_SYMBOL_GPL(dev_fill_bridge_path);
>> +
>> +int dev_fill_forward_path(const struct net_device *dev, const u8 *daddr,
>> +			  struct net_device_path_stack *stack)
>> +{
>> +	struct net_device_path_ctx ctx = {
>> +		.dev	= dev,
>> +	};
>> +
>> +	memcpy(ctx.daddr, daddr, sizeof(ctx.daddr));
>> +
>> +	stack->num_paths = 0;
>> +
>> +	return dev_fill_forward_path_common(&ctx, stack);
>> +}
>>  EXPORT_SYMBOL_GPL(dev_fill_forward_path);
>>  
>>  /**
>