Message-ID: <5c8a286b-932b-135f-5da4-68d18cfcb891@chinatelecom.cn>
Date:   Fri, 14 Jan 2022 17:07:04 +0800
From:   孙守鑫 <sunshouxin@...natelecom.cn>
To:     Jay Vosburgh <jay.vosburgh@...onical.com>
Cc:     vfalico@...il.com, andy@...yhouse.net, davem@...emloft.net,
        kuba@...nel.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, huyd12@...natelecom.cn
Subject: Re: [RESEND PATCH v5] net: bonding: Add support for IPV6 ns/na to
 balance-alb/balance-tlb mode


在 2022/1/11 3:23, Jay Vosburgh 写道:
> 	I'm getting back to this after the holiday break, and have some
> follow up from our prior discussions that I'll paste in below.
>
> Sun Shouxin <sunshouxin@...natelecom.cn> wrote:
>
>> Since ipv6 neighbor solicitation and advertisement messages
>> isn't handled gracefully in bonding6 driver, we can see packet
>> drop due to inconsistency bewteen mac address in the option
>> message and source MAC .
>>
>> Another examples is ipv6 neighbor solicitation and advertisement
>> messages from VM via tap attached to host brighe, the src mac
>> mighe be changed through balance-alb mode, but it is not synced
>> with Link-layer address in the option message.
>>
>> The patch implements bond6's tx handle for ipv6 neighbor
>> solicitation and advertisement messages.
>>> 	I'm not sure what you've changed here for v5 as there's no
>>> changelog, but I believe the observed problems to be a transmit side
>>> effect (i.e., it is induced by the balance-tlb mode balancing of
>>> outgoing traffic).  As such, the tlb side will rebalance all of the
>>> traffic every ten seconds, so any MAC ND_OPT_*_LL_ADDR option
>>> assignments in the outgoing NS/NA datagrams will only be valid for that
>>> length of time, correct?
>> Yes,  MAC ND_OPT_*_LL_ADDR option assignments in the outgoing NS/NA
>> datagrams will only be valid for that length of time ,and then,
>> it will be inconsistensy in the next ten seconds.
> 	So, presumably then the original issue (with the topology
> diagram that's now omitted) can recur 10 seconds later (after a TLB
> rebalance)?  If so, I don't understand why this patch is an improvement.
>
>>> 	In any event, my real question is whether simply disabling tlb
>>> balancing for NS/NA datagrams will resolve the observed issues (i.e.,
>>> have bond_xmit_tlb_slave_get return NULL for IPv6 NS/NA datagrams).
>>> Doing so will cause all NS/NA traffic to egress through the active
>>> interface.  There's already a test in your logic to check for the
>>> tx_slave != bond->curr_active_slave, so presumably everything works
>>> correctly if the NS/NA goes out on the curr_active_slave.  If the "edit
>>> NS/NA datagrams" solution works even in the face of rebalance of
>>> traffic, then would simply assigning all NS/NA traffic to the
>>> curr_active_slave eliminate the problem?
>> Yes, assigning all Ns/Na traffic to the curr_active_slave can resolve the
>> difference between mac in the Ns/Na options with the source mac.
>> But this makes the rlb doesn't work in the alb mode,
>> one interface with bond6 will not receive any ingress packets.
>> It is mismatch Bond6 specification.
> 	Does assigning all NS/NA to the curr_active_slave avoid the
> inconsistency when a TLB side rebalance occurs?  I believe it should,
> but want to confirm.
>
> 	As for the RLB functionality (i.e., the balance-alb remote to
> local load balance), that is not implemented for IPv6 and this patch is
> not providing an implementation of the RLB logic for IPv6, so I'm
> unclear why you expect it to work, or what the "mismatch Bond6
> specification" is.
>
> 	To be clear, implementing RLB for IPv6 would include what this
> patch is doing (adjusting the content of NS/NA datagrams), but a
> complete implementation requires additional logic that isn't here, e.g.,
> adding IPv6 logic to the RLB rebalance code, connecting NS/NA
> manipulation to rlb_choose_channel(), and likely other things that don't
> come immediately to mind.
>
> 	In summary, it sounds to me like the actual bug originally
> reported (with the now-omitted diagram) would be resolved by assigning
> NS/NA datagrams to the curr_active_slave, and supporting RLB for IPv6 is
> a larger project than what's provided by this patch.  Am I understanding
> correctly?


Thanks your comment.
For the simplify, I would like to resolve the inconsistent mac at first 
by assigning NS/NA datagrams to the curr_active_slave by V6 soon.
Supporting RLB for IPv6, it looks like hard a bit and I wonder if we can 
resolve it in another patch？
any comments?


>
> 	-J
>
>> Suggested-by: Hu Yadi <huyd12@...natelecom.cn>
>> Reported-by: kernel test robot <lkp@...el.com>
>> Signed-off-by: Sun Shouxin <sunshouxin@...natelecom.cn>
>> ---
>> drivers/net/bonding/bond_alb.c | 149 +++++++++++++++++++++++++++++++++
>> 1 file changed, 149 insertions(+)
>>
>> diff --git a/drivers/net/bonding/bond_alb.c b/drivers/net/bonding/bond_alb.c
>> index 533e476988f2..485e4863a365 100644
>> --- a/drivers/net/bonding/bond_alb.c
>> +++ b/drivers/net/bonding/bond_alb.c
>> @@ -22,6 +22,8 @@
>> #include <asm/byteorder.h>
>> #include <net/bonding.h>
>> #include <net/bond_alb.h>
>> +#include <net/ndisc.h>
>> +#include <net/ip6_checksum.h>
>>
>> static const u8 mac_v6_allmcast[ETH_ALEN + 2] __long_aligned = {
>> 	0x33, 0x33, 0x00, 0x00, 0x00, 0x01
>> @@ -1269,6 +1271,137 @@ static int alb_set_mac_address(struct bonding *bond, void *addr)
>> 	return res;
>> }
>>
>> +/*determine if the packet is NA or NS*/
>> +static bool __alb_determine_nd(struct icmp6hdr *hdr)
>> +{
>> +	if (hdr->icmp6_type == NDISC_NEIGHBOUR_ADVERTISEMENT ||
>> +	    hdr->icmp6_type == NDISC_NEIGHBOUR_SOLICITATION) {
>> +		return true;
>> +	}
>> +
>> +	return false;
>> +}
>> +
>> +static void alb_change_nd_option(struct sk_buff *skb, void *data)
>> +{
>> +	struct nd_msg *msg = (struct nd_msg *)skb_transport_header(skb);
>> +	struct nd_opt_hdr *nd_opt = (struct nd_opt_hdr *)msg->opt;
>> +	struct net_device *dev = skb->dev;
>> +	struct icmp6hdr *icmp6h = icmp6_hdr(skb);
>> +	struct ipv6hdr *ip6hdr = ipv6_hdr(skb);
>> +	u8 *lladdr = NULL;
>> +	u32 ndoptlen = skb_tail_pointer(skb) - (skb_transport_header(skb) +
>> +				offsetof(struct nd_msg, opt));
>> +
>> +	while (ndoptlen) {
>> +		int l;
>> +
>> +		switch (nd_opt->nd_opt_type) {
>> +		case ND_OPT_SOURCE_LL_ADDR:
>> +		case ND_OPT_TARGET_LL_ADDR:
>> +			lladdr = ndisc_opt_addr_data(nd_opt, dev);
>> +			break;
>> +
>> +		default:
>> +			lladdr = NULL;
>> +			break;
>> +		}
>> +
>> +		l = nd_opt->nd_opt_len << 3;
>> +
>> +		if (ndoptlen < l || l == 0)
>> +			return;
>> +
>> +		if (lladdr) {
>> +			memcpy(lladdr, data, dev->addr_len);
>> +			icmp6h->icmp6_cksum = 0;
>> +
>> +			icmp6h->icmp6_cksum = csum_ipv6_magic(&ip6hdr->saddr,
>> +							      &ip6hdr->daddr,
>> +						ntohs(ip6hdr->payload_len),
>> +						IPPROTO_ICMPV6,
>> +						csum_partial(icmp6h,
>> +							     ntohs(ip6hdr->payload_len), 0));
>> +			return;
>> +		}
>> +		ndoptlen -= l;
>> +		nd_opt = ((void *)nd_opt) + l;
>> +	}
>> +}
>> +
>> +static u8 *alb_get_lladdr(struct sk_buff *skb)
>> +{
>> +	struct nd_msg *msg = (struct nd_msg *)skb_transport_header(skb);
>> +	struct nd_opt_hdr *nd_opt = (struct nd_opt_hdr *)msg->opt;
>> +	struct net_device *dev = skb->dev;
>> +	u8 *lladdr = NULL;
>> +	u32 ndoptlen = skb_tail_pointer(skb) - (skb_transport_header(skb) +
>> +				offsetof(struct nd_msg, opt));
>> +
>> +	while (ndoptlen) {
>> +		int l;
>> +
>> +		switch (nd_opt->nd_opt_type) {
>> +		case ND_OPT_SOURCE_LL_ADDR:
>> +		case ND_OPT_TARGET_LL_ADDR:
>> +			lladdr = ndisc_opt_addr_data(nd_opt, dev);
>> +			break;
>> +
>> +		default:
>> +			break;
>> +		}
>> +
>> +		l = nd_opt->nd_opt_len << 3;
>> +
>> +		if (ndoptlen < l || l == 0)
>> +			return NULL;
>> +
>> +		if (lladdr)
>> +			return lladdr;
>> +
>> +		ndoptlen -= l;
>> +		nd_opt = ((void *)nd_opt) + l;
>> +	}
>> +
>> +	return lladdr;
>> +}
>> +
>> +static void alb_set_nd_option(struct sk_buff *skb, struct bonding *bond,
>> +			      struct slave *tx_slave)
>> +{
>> +	struct ipv6hdr *ip6hdr;
>> +	struct icmp6hdr *hdr;
>> +
>> +	if (skb->protocol == htons(ETH_P_IPV6)) {
>> +		if (tx_slave && tx_slave !=
>> +		    rcu_access_pointer(bond->curr_active_slave)) {
>> +			ip6hdr = ipv6_hdr(skb);
>> +			if (ip6hdr->nexthdr == IPPROTO_ICMPV6) {
>> +				hdr = icmp6_hdr(skb);
>> +				if (__alb_determine_nd(hdr))
>> +					alb_change_nd_option(skb, tx_slave->dev->dev_addr);
>> +			}
>> +		}
>> +	}
>> +}
>> +
>> +static bool alb_determine_nd(struct sk_buff *skb, struct bonding *bond)
>> +{
>> +	struct ipv6hdr *ip6hdr;
>> +	struct icmp6hdr *hdr;
>> +
>> +	if (skb->protocol == htons(ETH_P_IPV6)) {
>> +		ip6hdr = ipv6_hdr(skb);
>> +		if (ip6hdr->nexthdr == IPPROTO_ICMPV6) {
>> +			hdr = icmp6_hdr(skb);
>> +			if (__alb_determine_nd(hdr))
>> +				return true;
>> +		}
>> +	}
>> +
>> +	return false;
>> +}
>> +
>> /************************ exported alb functions ************************/
>>
>> int bond_alb_initialize(struct bonding *bond, int rlb_enabled)
>> @@ -1350,6 +1483,9 @@ struct slave *bond_xmit_tlb_slave_get(struct bonding *bond,
>> 		switch (skb->protocol) {
>> 		case htons(ETH_P_IP):
>> 		case htons(ETH_P_IPV6):
>> +			if (alb_determine_nd(skb, bond))
>> +				break;
>> +
>> 			hash_index = bond_xmit_hash(bond, skb);
>> 			if (bond->params.tlb_dynamic_lb) {
>> 				tx_slave = tlb_choose_channel(bond,
>> @@ -1446,6 +1582,18 @@ struct slave *bond_xmit_alb_slave_get(struct bonding *bond,
>> 			break;
>> 		}
>>
>> +		if (alb_determine_nd(skb, bond)) {
>> +			u8 *lladdr;
>> +
>> +			lladdr = alb_get_lladdr(skb);
>> +			if (lladdr) {
>> +				if (!bond_slave_has_mac_rx(bond, lladdr)) {
>> +					do_tx_balance = false;
>> +					break;
>> +				}
>> +			}
>> +		}
>> +
>> 		hash_start = (char *)&ip6hdr->daddr;
>> 		hash_size = sizeof(ip6hdr->daddr);
>> 		break;
>> @@ -1489,6 +1637,7 @@ netdev_tx_t bond_alb_xmit(struct sk_buff *skb, struct net_device *bond_dev)
>> 	struct slave *tx_slave = NULL;
>>
>> 	tx_slave = bond_xmit_alb_slave_get(bond, skb);
>> +	alb_set_nd_option(skb, bond, tx_slave);
>> 	return bond_do_alb_xmit(skb, bond, tx_slave);
>> }
>>
>>
>> base-commit: 7a29b11da9651ef6a970e2f6bfd276f053aeb06a
>> -- 
>> 2.27.0
>>
> ---
> 	-Jay Vosburgh, jay.vosburgh@...onical.com

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