Date:   Thu, 28 Oct 2021 01:12:07 +0900
From:   Taehee Yoo <ap420073@...il.com>
To:     David Ahern <dsahern@...il.com>, davem@...emloft.net,
        kuba@...nel.org, dsahern@...nel.org, netdev@...r.kernel.org
Cc:     dkirjanov@...e.de
Subject: Re: [PATCH net-next 2/4 v4] amt: add data plane of amt interface

Hi, David,
Thank you for your review!

On 10/28/21 12:00 AM, David Ahern wrote:
 > On 10/26/21 9:10 AM, Taehee Yoo wrote:
 >> diff --git a/drivers/net/amt.c b/drivers/net/amt.c
 >> index 8d4782c66cde..c3ac94b6d3e8 100644
 >> --- a/drivers/net/amt.c
 >> +++ b/drivers/net/amt.c
 >> @@ -31,6 +31,1220 @@
 >>
 >>   static struct workqueue_struct *amt_wq;
 >>
 >> +static char *status_str[] = {
 >> +	"AMT_STATUS_INIT",
 >> +	"AMT_STATUS_SENT_DISCOVERY",
 >> +	"AMT_STATUS_RECEIVED_DISCOVERY",
 >> +	"AMT_STATUS_SENT_ADVERTISEMENT",
 >> +	"AMT_STATUS_RECEIVED_ADVERTISEMENT",
 >> +	"AMT_STATUS_SENT_REQUEST",
 >> +	"AMT_STATUS_RECEIVED_REQUEST",
 >> +	"AMT_STATUS_SENT_QUERY",
 >> +	"AMT_STATUS_RECEIVED_QUERY",
 >> +	"AMT_STATUS_SENT_UPDATE",
 >> +	"AMT_STATUS_RECEIVED_UPDATE",
 >> +};
 >> +
 >> +static char *type_str[] = {
 >> +	"AMT_MSG_DISCOVERY",
 >> +	"AMT_MSG_ADVERTISEMENT",
 >> +	"AMT_MSG_REQUEST",
 >> +	"AMT_MSG_MEMBERSHIP_QUERY",
 >> +	"AMT_MSG_MEMBERSHIP_UPDATE",
 >> +	"AMT_MSG_MULTICAST_DATA",
 >> +	"AMT_MSG_TEATDOWM",
 >
 > TEARDOWN is misspelled.
 >

Okay, I will fix it.

 >> +};
 >> +
 >> +static struct amt_skb_cb *amt_skb_cb(struct sk_buff *skb)
 >> +{
 >> +	return (struct amt_skb_cb *)((void *)skb->cb +
 >> +		sizeof(struct qdisc_skb_cb));
 >
 > how will you know of sizeof(struct qdisc_skb_cb) + sizeof(struct
 > amt_skb_cb) exceeds the cb space? You should add a BUILD_BUG_ON.
 >

Thanks, I will add BUILD_BUG_ON.

 >
 >> +}
 >> +
 >> +static struct sk_buff *amt_build_igmp_gq(struct amt_dev *amt)
 >> +{
 >> +	int hlen = LL_RESERVED_SPACE(amt->dev);
 >> +	int tlen = amt->dev->needed_tailroom;
 >> +	struct igmpv3_query *ihv3;
 >> +	void *csum_start = NULL;
 >> +	__sum16 *csum = NULL;
 >> +	struct sk_buff *skb;
 >> +	struct ethhdr *eth;
 >> +	struct iphdr *iph;
 >> +	unsigned int len;
 >> +	int offset;
 >> +
 >> +	len = hlen + tlen + sizeof(*iph) + 4 + sizeof(*ihv3);
 >> +	skb = netdev_alloc_skb_ip_align(amt->dev, len);
 >> +	if (!skb)
 >> +		return NULL;
 >> +
 >> +	skb_reserve(skb, hlen);
 >> +	skb_push(skb, sizeof(*eth));
 >> +	skb->protocol = htons(ETH_P_IP);
 >> +	skb_reset_mac_header(skb);
 >> +	skb->priority = TC_PRIO_CONTROL;
 >> +	skb_put(skb, sizeof(*iph) + 4 + sizeof(*ihv3));
 >> +	skb_pull(skb, sizeof(*eth));
 >> +	skb_reset_network_header(skb);
 >> +
 >> +	iph		= ip_hdr(skb);
 >> +	iph->version	= 4;
 >> +	iph->ihl	= (sizeof(struct iphdr) + 4) >> 2;
 >> +	iph->tos	= 0xc0;
 >> +	iph->tot_len	= htons(sizeof(*iph) + 4 + sizeof(*ihv3));
 >> +	iph->frag_off	= htons(IP_DF);
 >> +	iph->ttl	= 1;
 >> +	iph->id		= 0;
 >> +	iph->protocol	= IPPROTO_IGMP;
 >> +	iph->daddr	= htonl(INADDR_ALLHOSTS_GROUP);
 >> +	iph->saddr	= htonl(INADDR_ANY);
 >> +	((u8 *)&iph[1])[0] = IPOPT_RA;
 >> +	((u8 *)&iph[1])[1] = 4;
 >> +	((u8 *)&iph[1])[2] = 0;
 >> +	((u8 *)&iph[1])[3] = 0;
 >
 > This reads weird to me. Why not use a local variable like:
 > #define AMT_IPHDR_OPTS 4
 > 	u8 buf[AMT_IPHDR_OPTS] = (u8 *)(iph + 1);
 >
 > and then use AMT_IPHDR_OPTS in place of the magic '4' in the skb
 > manipulations.
 >

Thanks, I will use what you suggested.

 >> +	ip_send_check(iph);
 >> +
 >> +	eth = eth_hdr(skb);
 >> +	ether_addr_copy(eth->h_source, amt->dev->dev_addr);
 >> +	ip_eth_mc_map(htonl(INADDR_ALLHOSTS_GROUP), eth->h_dest);
 >> +	eth->h_proto = htons(ETH_P_IP);
 >> +
 >> +	ihv3		= skb_pull(skb, sizeof(*iph) + 4);
 >> +	skb_reset_transport_header(skb);
 >> +	ihv3->type	= IGMP_HOST_MEMBERSHIP_QUERY;
 >> +	ihv3->code	= 1;
 >> +	ihv3->group	= 0;
 >> +	ihv3->qqic	= amt->qi;
 >> +	ihv3->nsrcs	= 0;
 >> +	ihv3->resv	= 0;
 >> +	ihv3->suppress	= false;
 >> +	ihv3->qrv	= amt->net->ipv4.sysctl_igmp_qrv;
 >> +	ihv3->csum	= 0;
 >> +	csum		= &ihv3->csum;
 >> +	csum_start	= (void *)ihv3;
 >> +	*csum		= ip_compute_csum(csum_start, sizeof(*ihv3));
 >> +	offset		= skb_transport_offset(skb);
 >> +	skb->csum	= skb_checksum(skb, offset, skb->len - offset, 0);
 >> +	skb->ip_summed	= CHECKSUM_NONE;
 >> +
 >> +	skb_push(skb, sizeof(*eth) + sizeof(*iph) + 4);
 >> +
 >> +	return skb;
 >> +}
 >> +
 >
 >
 >
 >> +static void amt_send_request(struct amt_dev *amt, bool v6)
 >> +{
 >> +	struct amt_header_request *amtrh;
 >> +	int hlen, tlen, offset;
 >> +	struct socket *sock;
 >> +	struct udphdr *udph;
 >> +	struct sk_buff *skb;
 >> +	struct iphdr *iph;
 >> +	struct rtable *rt;
 >> +	struct flowi4 fl4;
 >> +	u32 len;
 >> +	int err;
 >> +
 >> +	rcu_read_lock();
 >> +	sock = rcu_dereference(amt->sock);
 >> +	if (!sock)
 >> +		goto out;
 >> +
 >> +	if (!netif_running(amt->stream_dev) || !netif_running(amt->dev))
 >> +		goto out;
 >> +
 >> +	rt = ip_route_output_ports(amt->net, &fl4, sock->sk,
 >> +				   amt->remote_ip, amt->local_ip,
 >> +				   amt->gw_port, amt->relay_port,
 >> +				   IPPROTO_UDP, 0,
 >> +				   amt->stream_dev->ifindex);
 >> +	if (IS_ERR(rt)) {
 >> +		amt->dev->stats.tx_errors++;
 >> +		goto out;
 >> +	}
 >> +
 >> +	hlen = LL_RESERVED_SPACE(amt->dev);
 >> +	tlen = amt->dev->needed_tailroom;
 >> +	len = hlen + tlen + sizeof(*iph) + sizeof(*udph) + sizeof(*amtrh);
 >> +	skb = netdev_alloc_skb_ip_align(amt->dev, len);
 >> +	if (!skb) {
 >> +		ip_rt_put(rt);
 >> +		amt->dev->stats.tx_errors++;
 >> +		goto out;
 >> +	}
 >> +
 >> +	skb->priority = TC_PRIO_CONTROL;
 >> +	skb_dst_set(skb, &rt->dst);
 >> +
 >> +	len = sizeof(*iph) + sizeof(*udph) + sizeof(*amtrh);
 >> +	skb_reset_network_header(skb);
 >> +	skb_put(skb, len);
 >> +	amtrh = skb_pull(skb, sizeof(*iph) + sizeof(*udph));
 >> +	amtrh->version	 = 0;
 >> +	amtrh->type	 = AMT_MSG_REQUEST;
 >> +	amtrh->reserved1 = 0;
 >> +	amtrh->p	 = v6;
 >> +	amtrh->reserved2 = 0;
 >> +	amtrh->nonce	 = amt->nonce;
 >> +	skb_push(skb, sizeof(*udph));
 >> +	skb_reset_transport_header(skb);
 >> +	udph		= udp_hdr(skb);
 >> +	udph->source	= amt->gw_port;
 >> +	udph->dest	= amt->relay_port;
 >> +	udph->len	= htons(sizeof(*amtrh) + sizeof(*udph));
 >> +	udph->check	= 0;
 >> +	offset = skb_transport_offset(skb);
 >> +	skb->csum = skb_checksum(skb, offset, skb->len - offset, 0);
 >> +	udph->check = csum_tcpudp_magic(amt->local_ip, amt->remote_ip,
 >> +					sizeof(*udph) + sizeof(*amtrh),
 >> +					IPPROTO_UDP, skb->csum);
 >> +
 >> +	skb_push(skb, sizeof(*iph));
 >> +	iph		= ip_hdr(skb);
 >> +	iph->version	= 4;
 >> +	iph->ihl	= (sizeof(struct iphdr)) >> 2;
 >> +	iph->tos	= 0xc0;
 >
 > why c0? Use a macro with a proper name.
 >

Okay, I will make a new macro.

 >> +	iph->frag_off	= 0;
 >> +	iph->ttl	= ip4_dst_hoplimit(&rt->dst);
 >> +	iph->daddr	= amt->remote_ip;
 >> +	iph->saddr	= amt->local_ip;
 >> +	iph->protocol	= IPPROTO_UDP;
 >> +	iph->tot_len	= htons(len);
 >> +
 >> +	skb->ip_summed = CHECKSUM_NONE;
 >> +	ip_select_ident(amt->net, skb, NULL);
 >> +	ip_send_check(iph);
 >> +	err = ip_local_out(amt->net, sock->sk, skb);
 >> +	if (unlikely(net_xmit_eval(err)))
 >> +		amt->dev->stats.tx_errors++;
 >> +
 >> +out:
 >> +	rcu_read_unlock();
 >> +}
 >> +
 >> +static void amt_send_igmp_gq(struct amt_dev *amt,
 >> +			     struct amt_tunnel_list *tunnel)
 >> +{
 >> +	struct sk_buff *skb;
 >> +
 >> +	skb = amt_build_igmp_gq(amt);
 >> +	if (!skb)
 >> +		return;
 >> +
 >> +	amt_skb_cb(skb)->tunnel = tunnel;
 >> +	dev_queue_xmit(skb);
 >> +}
 >> +
 >
 >> +
 >> +static netdev_tx_t amt_dev_xmit(struct sk_buff *skb, struct 
net_device *dev)
 >> +{
 >> +	struct amt_dev *amt = netdev_priv(dev);
 >> +	struct amt_tunnel_list *tunnel;
 >> +	bool report = false;
 >> +	struct igmphdr *ih;
 >> +	bool query = false;
 >> +	struct iphdr *iph;
 >> +	bool data = false;
 >> +	bool v6 = false;
 >> +
 >> +	rcu_read_lock();
 >
 > As I recall ndo_start_xmit functions are called inside of
 > rcu_read_lock_bh().
 >
 >

Thanks, I checked out it.
dev_queue_xmit() hold rcu_read_lock_bh() then it calls ->ndo_start_xmit().
I will remove it.

 >> +	iph = ip_hdr(skb);> +	if (iph->version == 4) {
 >> +		if (!ipv4_is_multicast(iph->daddr))
 >> +			goto free;
 >> +
 >> +		if (!ip_mc_check_igmp(skb)) {
 >> +			ih = igmp_hdr(skb);
 >> +			switch (ih->type) {
 >> +			case IGMPV3_HOST_MEMBERSHIP_REPORT:
 >> +			case IGMP_HOST_MEMBERSHIP_REPORT:
 >> +				report = true;
 >> +				break;
 >> +			case IGMP_HOST_MEMBERSHIP_QUERY:
 >> +				query = true;
 >> +				break;
 >> +			default:
 >> +				goto free;
 >> +			}
 >> +		} else {
 >> +			data = true;
 >> +		}
 >> +		v6 = false;
 >> +	} else {
 >> +		dev->stats.tx_errors++;
 >> +		goto free;
 >> +	}
 >> +
 >> +	if (!pskb_may_pull(skb, sizeof(struct ethhdr)))
 >> +		goto free;
 >> +
 >> +	skb_pull(skb, sizeof(struct ethhdr));
 >> +
 >> +	if (amt->mode == AMT_MODE_GATEWAY) {
 >> +		/* Gateway only passes IGMP/MLD packets */
 >> +		if (!report)
 >> +			goto free;
 >> +		if ((!v6 && !amt->ready4) || (v6 && !amt->ready6))
 >> +			goto free;
 >> +		if (amt_send_membership_update(amt, skb,  v6))
 >> +			goto free;
 >> +		goto unlock;
 >> +	} else if (amt->mode == AMT_MODE_RELAY) {
 >> +		if (query) {
 >> +			tunnel = amt_skb_cb(skb)->tunnel;
 >> +			if (!tunnel) {
 >> +				WARN_ON(1);
 >> +				goto free;
 >> +			}
 >> +
 >> +			/* Do not forward unexpected query */
 >> +			if (amt_send_membership_query(amt, skb, tunnel, v6))
 >> +				goto free;
 >> +			goto unlock;
 >> +		}
 >> +
 >> +		if (!data)
 >> +			goto free;
 >> +		list_for_each_entry_rcu(tunnel, &amt->tunnel_list, list)
 >> +			amt_send_multicast_data(amt, skb, tunnel, v6);
 >> +	}
 >> +
 >> +	dev_kfree_skb(skb);
 >> +	rcu_read_unlock();
 >> +	return NETDEV_TX_OK;
 >> +free:
 >> +	dev_kfree_skb(skb);
 >> +unlock:
 >> +	rcu_read_unlock();
 >> +	dev->stats.tx_dropped++;
 >> +	return NETDEV_TX_OK;
 >> +}
 >> +
 >
 >
 >
 >
 >> +static bool amt_request_handler(struct amt_dev *amt, struct sk_buff 
*skb)
 >> +{
 >> +	struct amt_header_request *amtrh;
 >> +	struct amt_tunnel_list *tunnel;
 >> +	unsigned long long key;
 >> +	struct udphdr *udph;
 >> +	struct iphdr *iph;
 >> +	u64 mac;
 >> +	int i;
 >> +
 >> +	if (!pskb_may_pull(skb, sizeof(*udph) + sizeof(*amtrh)))
 >> +		return true;
 >> +
 >> +	iph = ip_hdr(skb);
 >> +	udph = udp_hdr(skb);
 >> +	amtrh = (struct amt_header_request *)(udp_hdr(skb) + 1);
 >> +
 >> +	if (amtrh->reserved1 || amtrh->reserved2 || amtrh->version)
 >> +		return true;
 >> +
 >> +	list_for_each_entry_rcu(tunnel, &amt->tunnel_list, list)
 >> +		if (tunnel->ip4 == iph->saddr)
 >> +			goto send;
 >> +
 >> +	if (amt->nr_tunnels >= amt->max_tunnels) {
 >> +		icmp_ndo_send(skb, ICMP_DEST_UNREACH, ICMP_HOST_UNREACH, 0);
 >> +		return true;
 >> +	}
 >> +
 >> +	tunnel = kmalloc(sizeof(*tunnel) +
 >
 > kzalloc and then you do not need the '= 0' below.
 >

Thanks, I will use kzalloc instead of kmalloc.

 >> +			 (sizeof(struct hlist_head) * amt->hash_buckets),
 >> +			 GFP_ATOMIC);
 >> +	if (!tunnel)
 >> +		return true;
 >> +
 >> +	tunnel->source_port = udph->source;
 >> +	tunnel->ip4 = iph->saddr;
 >> +	tunnel->nr_groups = 0;
 >> +	tunnel->nr_sources = 0;
 >> +
 >> +	memcpy(&key, &tunnel->key, sizeof(unsigned long long));
 >> +	tunnel->reserved = 0;
 >> +	tunnel->amt = amt;
 >> +	spin_lock_init(&tunnel->lock);
 >> +	for (i = 0; i < amt->hash_buckets; i++)
 >> +		INIT_HLIST_HEAD(&tunnel->groups[i]);
 >> +
 >> +	INIT_DELAYED_WORK(&tunnel->gc_wq, amt_tunnel_expire);
 >> +
 >> +	spin_lock_bh(&amt->lock);
 >> +	list_add_tail_rcu(&tunnel->list, &amt->tunnel_list);
 >> +	tunnel->key = amt->key;
 >> +	amt_update_relay_status(tunnel, AMT_STATUS_RECEIVED_REQUEST, true);
 >> +	amt->nr_tunnels++;
 >> +	mod_delayed_work(amt_wq, &tunnel->gc_wq,
 >> +			 msecs_to_jiffies(amt_gmi(amt)));
 >> +	spin_unlock_bh(&amt->lock);
 >> +
 >> +send:
 >> +	tunnel->nonce = amtrh->nonce;
 >> +	mac = siphash_3u32((__force u32)tunnel->ip4,
 >> +			   (__force u32)tunnel->source_port,
 >> +			   (__force u32)tunnel->nonce,
 >> +			   &tunnel->key);
 >> +	tunnel->mac = mac >> 16;
 >> +
 >> +	if (!netif_running(amt->dev) || !netif_running(amt->stream_dev))
 >> +		return true;
 >> +
 >> +	if (!amtrh->p)
 >> +		amt_send_igmp_gq(amt, tunnel);
 >> +
 >> +	return false;
 >> +}
 >> +
 >
 > you create some selftests and include some torture cases around cleanup
 > of all the work activity.
 >

Okay, I will create selftests!

Thanks a lot for your review!

Thanks,
Taehee

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