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Date: Mon, 20 Dec 2021 07:05:10 -0800
From: Eric Dumazet <eric.dumazet@...il.com>
To: 孙守鑫 <sunshouxin@...natelecom.cn>,
Eric Dumazet <eric.dumazet@...il.com>, j.vosburgh@...il.com,
vfalico@...il.com, andy@...yhouse.net, davem@...emloft.net,
kuba@...nel.org
Cc: netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
huyd12@...natelecom.cn
Subject: Re: [PATCH V2] net: bonding: Add support for IPV6 ns/na
On 12/19/21 5:57 PM, 孙守鑫 wrote:
>
> 在 2021/12/14 16:05, Eric Dumazet 写道:
>>
>> On 12/10/21 5:08 AM, Sun Shouxin 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.
>>>
>>> Border-Leaf
>>> / \
>>> / \
>>> Tunnel1 Tunnel2
>>> / \
>>> / \
>>> Leaf-1--Tunnel3--Leaf-2
>>> \ /
>>> \ /
>>> \ /
>>> \ /
>>> NIC1 NIC2
>>> \ /
>>> server
>>>
>>> We can see in our lab the Border-Leaf receives occasionally
>>> a NA packet which is assigned to NIC1 mac in ND/NS option
>>> message, but actaully send out via NIC2 mac due to tx-alb,
>>> as a result, it will cause inconsistency between MAC table
>>> and ND Table in Border-Leaf, i.e, NIC1 = Tunnel2 in ND table
>>> and NIC1 = Tunnel1 in mac table.
>>>
>>> And then, Border-Leaf starts to forward packet destinated
>>> to the Server, it will only check the ND table entry in some
>>> switch to encapsulate the destination MAC of the message as
>>> NIC1 MAC, and then send it out from Tunnel2 by ND table.
>>> Then, Leaf-2 receives the packet, it notices the destination
>>> MAC of message is NIC1 MAC and should forword it to Tunne1
>>> by Tunnel3.
>>>
>>> However, this traffic forward will be failure due to split
>>> horizon of VxLAN tunnels.
>>>
>>> Suggested-by: Hu Yadi <huyd12@...natelecom.cn>
>>> Signed-off-by: Sun Shouxin <sunshouxin@...natelecom.cn>
>>> ---
>>> drivers/net/bonding/bond_alb.c | 131
>>> +++++++++++++++++++++++++++++++++++++++++
>>> 1 file changed, 131 insertions(+)
>>>
>>> diff --git a/drivers/net/bonding/bond_alb.c
>>> b/drivers/net/bonding/bond_alb.c
>>> index 533e476..afa386b 100644
>>> --- a/drivers/net/bonding/bond_alb.c
>>> +++ b/drivers/net/bonding/bond_alb.c
>>> @@ -22,6 +22,7 @@
>>> #include <asm/byteorder.h>
>>> #include <net/bonding.h>
>>> #include <net/bond_alb.h>
>>> +#include <net/ndisc.h>
>>> static const u8 mac_v6_allmcast[ETH_ALEN + 2] __long_aligned = {
>>> 0x33, 0x33, 0x00, 0x00, 0x00, 0x01
>>> @@ -1269,6 +1270,119 @@ 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);
>>
>> I am not sure it is allowed to change skb content without
>>
>> making sure skb ->head is private.
>>
>> (Think of tcpdump -i slaveX : we want to see the packet content
>> before your change)
>>
>> I would think skb_cow_head() or something similar is needed.
>>
>> This is tricky of course, since all cached pointers (icmp6h, ip6hdr,
>> msg, nd_opt)
>>
>> would need to be fetched again, since skb->head/data might be changed
>>
>> by skb_cow_head().
> The tcpdump should show the last packet which sent off from NIC in the
> end.
> could you light me up specific conditions?
I think I have been clear.
You can not modify skb->head unless it is allowed to.
tcpdump on the slave must show the exact packet being received,
before your modifications in bonding driver.
>>
>>
>>
>>
>>
>>> + 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));
>>> + }
>>> + 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 lladdr;
>>
>> return NULL ?
>>
>> (or risk out-of-bound access ?)
> Thanks your comment, I'll adjust it and send out V4 soon.
>>
>>> +
>>> + 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 = NULL;
>>> +
>>> + 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);
>>> + }
>>> + }
>>> + }
>>> +}
>>> +
>>> /************************ exported alb functions
>>> ************************/
>>> int bond_alb_initialize(struct bonding *bond, int rlb_enabled)
>>> @@ -1415,6 +1529,7 @@ struct slave *bond_xmit_alb_slave_get(struct
>>> bonding *bond,
>>> }
>>> case ETH_P_IPV6: {
>>> const struct ipv6hdr *ip6hdr;
>>> + struct icmp6hdr *hdr = NULL;
>>> /* IPv6 doesn't really use broadcast mac address, but leave
>>> * that here just in case.
>>> @@ -1446,6 +1561,21 @@ struct slave *bond_xmit_alb_slave_get(struct
>>> bonding *bond,
>>> break;
>>> }
>>> + if (ip6hdr->nexthdr == IPPROTO_ICMPV6) {
>>> + hdr = icmp6_hdr(skb);
>>> + if (alb_determine_nd(hdr)) {
>>> + u8 *lladdr = NULL;
>>> +
>>> + 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 +1619,7 @@ 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);
>>> }
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