* [PATCH 1/3] mptcp: fix warning in __skb_flow_dissect() when do syn cookie for subflow join
@ 2021-06-09 10:39 Jianguo Wu
2021-06-09 14:31 ` Paolo Abeni
0 siblings, 1 reply; 3+ messages in thread
From: Jianguo Wu @ 2021-06-09 10:39 UTC (permalink / raw)
To: mptcp; +Cc: Paolo Abeni, Florian Westphal
From: Jianguo Wu <wujianguo@chinatelecom.cn>
I got the following warning message while doing the test:
[ 55.552626] TCP: request_sock_subflow: Possible SYN flooding on port 8099. Sending cookies. Check SNMP counters.
[ 55.553024] ------------[ cut here ]------------
[ 55.553027] WARNING: CPU: 0 PID: 10 at net/core/flow_dissector.c:984 __skb_flow_dissect+0x280/0x1650
...
[ 55.553117] CPU: 0 PID: 10 Comm: ksoftirqd/0 Not tainted 5.12.0+ #18
[ 55.553121] Hardware name: VMware, Inc. VMware Virtual Platform/440BX Desktop Reference Platform, BIOS 6.00 02/27/2020
[ 55.553124] RIP: 0010:__skb_flow_dissect+0x280/0x1650
...
[ 55.553133] RSP: 0018:ffffb79580087770 EFLAGS: 00010246
[ 55.553137] RAX: 0000000000000000 RBX: ffffffff8ddb58e0 RCX: ffffb79580087888
[ 55.553139] RDX: ffffffff8ddb58e0 RSI: ffff8f7e4652b600 RDI: 0000000000000000
[ 55.553141] RBP: ffffb79580087858 R08: 0000000000000000 R09: 0000000000000008
[ 55.553143] R10: 000000008c622965 R11: 00000000d3313a5b R12: ffff8f7e4652b600
[ 55.553146] R13: ffff8f7e465c9062 R14: 0000000000000000 R15: ffffb79580087888
[ 55.553149] FS: 0000000000000000(0000) GS:ffff8f7f75e00000(0000) knlGS:0000000000000000
[ 55.553152] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 55.553154] CR2: 00007f73d1d19000 CR3: 0000000135e10004 CR4: 00000000003706f0
[ 55.553160] Call Trace:
[ 55.553166] ? __sha256_final+0x67/0xd0
[ 55.553173] ? sha256+0x7e/0xa0
[ 55.553177] __skb_get_hash+0x57/0x210
[ 55.553182] subflow_init_req_cookie_join_save+0xac/0xc0
[ 55.553189] subflow_check_req+0x474/0x550
[ 55.553195] ? ip_route_output_key_hash+0x67/0x90
[ 55.553200] ? xfrm_lookup_route+0x1d/0xa0
[ 55.553207] subflow_v4_route_req+0x8e/0xd0
[ 55.553212] tcp_conn_request+0x31e/0xab0
[ 55.553218] ? selinux_socket_sock_rcv_skb+0x116/0x210
[ 55.553224] ? tcp_rcv_state_process+0x179/0x6d0
[ 55.553229] tcp_rcv_state_process+0x179/0x6d0
[ 55.553235] tcp_v4_do_rcv+0xaf/0x220
[ 55.553239] tcp_v4_rcv+0xce4/0xd80
[ 55.553243] ? ip_route_input_rcu+0x246/0x260
[ 55.553248] ip_protocol_deliver_rcu+0x35/0x1b0
[ 55.553253] ip_local_deliver_finish+0x44/0x50
[ 55.553258] ip_local_deliver+0x6c/0x110
[ 55.553262] ? ip_rcv_finish_core.isra.19+0x5a/0x400
[ 55.553267] ip_rcv+0xd1/0xe0
...
After debugging, I found in __skb_flow_dissect(), skb->dev and skb->sk are both NULL,
then net is NULL, and trigger WARN_ON_ONCE(!net), actually net is always NULL in this
code path, as skb->dev is set to NULL in tcp_v4_rcv(), and skb->sk is never set.
Code snippet in __skb_flow_dissect() that trigger warning:
975 if (skb) {
976 if (!net) {
977 if (skb->dev)
978 net = dev_net(skb->dev);
979 else if (skb->sk)
980 net = sock_net(skb->sk);
981 }
982 }
983
984 WARN_ON_ONCE(!net);
So, if the skb->hash is not available, then fallback to use 4-tuple derived hash.
Fixes: 9466a1ccebbe("mptcp: enable JOIN requests even if cookies are in use").
Suggested-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Jianguo Wu <wujianguo@chinatelecom.cn>
---
net/mptcp/syncookies.c | 24 +++++++++++++++++++++++-
1 file changed, 23 insertions(+), 1 deletion(-)
diff --git a/net/mptcp/syncookies.c b/net/mptcp/syncookies.c
index abe0fd0..778bdba 100644
--- a/net/mptcp/syncookies.c
+++ b/net/mptcp/syncookies.c
@@ -35,9 +35,31 @@ struct join_entry {
static struct join_entry join_entries[COOKIE_JOIN_SLOTS] __cacheline_aligned_in_smp;
static spinlock_t join_entry_locks[COOKIE_JOIN_SLOTS] __cacheline_aligned_in_smp;
+static u32 mptcp_join_hashfn(const struct net *net, const __be32 laddr,
+ const __be16 lport, const __be32 faddr,
+ const __be16 fport)
+{
+ static u32 mptcp_join_hash_secret __read_mostly;
+
+ net_get_random_once(&mptcp_join_hash_secret, sizeof(mptcp_join_hash_secret));
+
+ return jhash_3words((__force __u32) laddr,
+ (__force __u32) faddr,
+ ((__u32) lport) << 16 | (__force __u32)fport,
+ mptcp_join_hash_secret + net_hash_mix(net));
+}
+
static u32 mptcp_join_entry_hash(struct sk_buff *skb, struct net *net)
{
- u32 i = skb_get_hash(skb) ^ net_hash_mix(net);
+ u32 i;
+ struct iphdr *iph = ip_hdr(skb);
+ struct tcphdr *th = tcp_hdr(skb);
+
+ if (!skb_get_hash_raw(skb))
+ i = mptcp_join_hashfn(net, iph->daddr, th->dest,
+ iph->saddr, th->source);
+ else
+ i = skb_get_hash_raw(skb) ^ net_hash_mix(net);
return i % ARRAY_SIZE(join_entries);
}
--
1.8.3.1
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH 1/3] mptcp: fix warning in __skb_flow_dissect() when do syn cookie for subflow join
2021-06-09 10:39 [PATCH 1/3] mptcp: fix warning in __skb_flow_dissect() when do syn cookie for subflow join Jianguo Wu
@ 2021-06-09 14:31 ` Paolo Abeni
2021-06-10 3:18 ` Jianguo Wu
0 siblings, 1 reply; 3+ messages in thread
From: Paolo Abeni @ 2021-06-09 14:31 UTC (permalink / raw)
To: Jianguo Wu, mptcp; +Cc: Florian Westphal
On Wed, 2021-06-09 at 18:39 +0800, Jianguo Wu wrote:
> From: Jianguo Wu <wujianguo@chinatelecom.cn>
>
> I got the following warning message while doing the test:
>
> [ 55.552626] TCP: request_sock_subflow: Possible SYN flooding on port 8099. Sending cookies. Check SNMP counters.
> [ 55.553024] ------------[ cut here ]------------
> [ 55.553027] WARNING: CPU: 0 PID: 10 at net/core/flow_dissector.c:984 __skb_flow_dissect+0x280/0x1650
> ...
> [ 55.553117] CPU: 0 PID: 10 Comm: ksoftirqd/0 Not tainted 5.12.0+ #18
> [ 55.553121] Hardware name: VMware, Inc. VMware Virtual Platform/440BX Desktop Reference Platform, BIOS 6.00 02/27/2020
> [ 55.553124] RIP: 0010:__skb_flow_dissect+0x280/0x1650
> ...
> [ 55.553133] RSP: 0018:ffffb79580087770 EFLAGS: 00010246
> [ 55.553137] RAX: 0000000000000000 RBX: ffffffff8ddb58e0 RCX: ffffb79580087888
> [ 55.553139] RDX: ffffffff8ddb58e0 RSI: ffff8f7e4652b600 RDI: 0000000000000000
> [ 55.553141] RBP: ffffb79580087858 R08: 0000000000000000 R09: 0000000000000008
> [ 55.553143] R10: 000000008c622965 R11: 00000000d3313a5b R12: ffff8f7e4652b600
> [ 55.553146] R13: ffff8f7e465c9062 R14: 0000000000000000 R15: ffffb79580087888
> [ 55.553149] FS: 0000000000000000(0000) GS:ffff8f7f75e00000(0000) knlGS:0000000000000000
> [ 55.553152] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> [ 55.553154] CR2: 00007f73d1d19000 CR3: 0000000135e10004 CR4: 00000000003706f0
> [ 55.553160] Call Trace:
> [ 55.553166] ? __sha256_final+0x67/0xd0
> [ 55.553173] ? sha256+0x7e/0xa0
> [ 55.553177] __skb_get_hash+0x57/0x210
> [ 55.553182] subflow_init_req_cookie_join_save+0xac/0xc0
> [ 55.553189] subflow_check_req+0x474/0x550
> [ 55.553195] ? ip_route_output_key_hash+0x67/0x90
> [ 55.553200] ? xfrm_lookup_route+0x1d/0xa0
> [ 55.553207] subflow_v4_route_req+0x8e/0xd0
> [ 55.553212] tcp_conn_request+0x31e/0xab0
> [ 55.553218] ? selinux_socket_sock_rcv_skb+0x116/0x210
> [ 55.553224] ? tcp_rcv_state_process+0x179/0x6d0
> [ 55.553229] tcp_rcv_state_process+0x179/0x6d0
> [ 55.553235] tcp_v4_do_rcv+0xaf/0x220
> [ 55.553239] tcp_v4_rcv+0xce4/0xd80
> [ 55.553243] ? ip_route_input_rcu+0x246/0x260
> [ 55.553248] ip_protocol_deliver_rcu+0x35/0x1b0
> [ 55.553253] ip_local_deliver_finish+0x44/0x50
> [ 55.553258] ip_local_deliver+0x6c/0x110
> [ 55.553262] ? ip_rcv_finish_core.isra.19+0x5a/0x400
> [ 55.553267] ip_rcv+0xd1/0xe0
> ...
>
> After debugging, I found in __skb_flow_dissect(), skb->dev and skb->sk are both NULL,
> then net is NULL, and trigger WARN_ON_ONCE(!net), actually net is always NULL in this
> code path, as skb->dev is set to NULL in tcp_v4_rcv(), and skb->sk is never set.
>
> Code snippet in __skb_flow_dissect() that trigger warning:
> 975 if (skb) {
> 976 if (!net) {
> 977 if (skb->dev)
> 978 net = dev_net(skb->dev);
> 979 else if (skb->sk)
> 980 net = sock_net(skb->sk);
> 981 }
> 982 }
> 983
> 984 WARN_ON_ONCE(!net);
>
> So, if the skb->hash is not available, then fallback to use 4-tuple derived hash.
>
> Fixes: 9466a1ccebbe("mptcp: enable JOIN requests even if cookies are in use").
> Suggested-by: Paolo Abeni <pabeni@redhat.com>
> Signed-off-by: Jianguo Wu <wujianguo@chinatelecom.cn>
> ---
> net/mptcp/syncookies.c | 24 +++++++++++++++++++++++-
> 1 file changed, 23 insertions(+), 1 deletion(-)
>
> diff --git a/net/mptcp/syncookies.c b/net/mptcp/syncookies.c
> index abe0fd0..778bdba 100644
> --- a/net/mptcp/syncookies.c
> +++ b/net/mptcp/syncookies.c
> @@ -35,9 +35,31 @@ struct join_entry {
> static struct join_entry join_entries[COOKIE_JOIN_SLOTS] __cacheline_aligned_in_smp;
> static spinlock_t join_entry_locks[COOKIE_JOIN_SLOTS] __cacheline_aligned_in_smp;
>
> +static u32 mptcp_join_hashfn(const struct net *net, const __be32 laddr,
> + const __be16 lport, const __be32 faddr,
> + const __be16 fport)
> +{
> + static u32 mptcp_join_hash_secret __read_mostly;
> +
> + net_get_random_once(&mptcp_join_hash_secret, sizeof(mptcp_join_hash_secret));
> +
> + return jhash_3words((__force __u32) laddr,
> + (__force __u32) faddr,
> + ((__u32) lport) << 16 | (__force __u32)fport,
> + mptcp_join_hash_secret + net_hash_mix(net));
> +}
> +
> static u32 mptcp_join_entry_hash(struct sk_buff *skb, struct net *net)
> {
> - u32 i = skb_get_hash(skb) ^ net_hash_mix(net);
> + u32 i;
> + struct iphdr *iph = ip_hdr(skb);
> + struct tcphdr *th = tcp_hdr(skb);
> +
> + if (!skb_get_hash_raw(skb))
> + i = mptcp_join_hashfn(net, iph->daddr, th->dest,
> + iph->saddr, th->source);
Here we need to handle ipv6 sockets/addresses, too. See sk_ehashfn()
in net/ipv4/inet_hashtables.c for some reference code.
There is an additional caveat I haven't thought before: teorically the
syn and the 3rd ack skbs could be received via different interfaces,
which will produce different skb->hash value. Or the NIC hash could be
teorically disabled (or enabled) in between.
TL;DR: I think we should always use the mptcp_join_hashfn() and never
look at skb->hash.
Sorry for the late feedback,
Paolo
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH 1/3] mptcp: fix warning in __skb_flow_dissect() when do syn cookie for subflow join
2021-06-09 14:31 ` Paolo Abeni
@ 2021-06-10 3:18 ` Jianguo Wu
0 siblings, 0 replies; 3+ messages in thread
From: Jianguo Wu @ 2021-06-10 3:18 UTC (permalink / raw)
To: Paolo Abeni, mptcp; +Cc: Florian Westphal
Hi Paolo,
On 2021/6/9 22:31, Paolo Abeni wrote:
> On Wed, 2021-06-09 at 18:39 +0800, Jianguo Wu wrote:
>> From: Jianguo Wu <wujianguo@chinatelecom.cn>
>>
>> I got the following warning message while doing the test:
>>
>> [ 55.552626] TCP: request_sock_subflow: Possible SYN flooding on port 8099. Sending cookies. Check SNMP counters.
>> [ 55.553024] ------------[ cut here ]------------
>> [ 55.553027] WARNING: CPU: 0 PID: 10 at net/core/flow_dissector.c:984 __skb_flow_dissect+0x280/0x1650
>> ...
>> [ 55.553117] CPU: 0 PID: 10 Comm: ksoftirqd/0 Not tainted 5.12.0+ #18
>> [ 55.553121] Hardware name: VMware, Inc. VMware Virtual Platform/440BX Desktop Reference Platform, BIOS 6.00 02/27/2020
>> [ 55.553124] RIP: 0010:__skb_flow_dissect+0x280/0x1650
>> ...
>> [ 55.553133] RSP: 0018:ffffb79580087770 EFLAGS: 00010246
>> [ 55.553137] RAX: 0000000000000000 RBX: ffffffff8ddb58e0 RCX: ffffb79580087888
>> [ 55.553139] RDX: ffffffff8ddb58e0 RSI: ffff8f7e4652b600 RDI: 0000000000000000
>> [ 55.553141] RBP: ffffb79580087858 R08: 0000000000000000 R09: 0000000000000008
>> [ 55.553143] R10: 000000008c622965 R11: 00000000d3313a5b R12: ffff8f7e4652b600
>> [ 55.553146] R13: ffff8f7e465c9062 R14: 0000000000000000 R15: ffffb79580087888
>> [ 55.553149] FS: 0000000000000000(0000) GS:ffff8f7f75e00000(0000) knlGS:0000000000000000
>> [ 55.553152] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>> [ 55.553154] CR2: 00007f73d1d19000 CR3: 0000000135e10004 CR4: 00000000003706f0
>> [ 55.553160] Call Trace:
>> [ 55.553166] ? __sha256_final+0x67/0xd0
>> [ 55.553173] ? sha256+0x7e/0xa0
>> [ 55.553177] __skb_get_hash+0x57/0x210
>> [ 55.553182] subflow_init_req_cookie_join_save+0xac/0xc0
>> [ 55.553189] subflow_check_req+0x474/0x550
>> [ 55.553195] ? ip_route_output_key_hash+0x67/0x90
>> [ 55.553200] ? xfrm_lookup_route+0x1d/0xa0
>> [ 55.553207] subflow_v4_route_req+0x8e/0xd0
>> [ 55.553212] tcp_conn_request+0x31e/0xab0
>> [ 55.553218] ? selinux_socket_sock_rcv_skb+0x116/0x210
>> [ 55.553224] ? tcp_rcv_state_process+0x179/0x6d0
>> [ 55.553229] tcp_rcv_state_process+0x179/0x6d0
>> [ 55.553235] tcp_v4_do_rcv+0xaf/0x220
>> [ 55.553239] tcp_v4_rcv+0xce4/0xd80
>> [ 55.553243] ? ip_route_input_rcu+0x246/0x260
>> [ 55.553248] ip_protocol_deliver_rcu+0x35/0x1b0
>> [ 55.553253] ip_local_deliver_finish+0x44/0x50
>> [ 55.553258] ip_local_deliver+0x6c/0x110
>> [ 55.553262] ? ip_rcv_finish_core.isra.19+0x5a/0x400
>> [ 55.553267] ip_rcv+0xd1/0xe0
>> ...
>>
>> After debugging, I found in __skb_flow_dissect(), skb->dev and skb->sk are both NULL,
>> then net is NULL, and trigger WARN_ON_ONCE(!net), actually net is always NULL in this
>> code path, as skb->dev is set to NULL in tcp_v4_rcv(), and skb->sk is never set.
>>
>> Code snippet in __skb_flow_dissect() that trigger warning:
>> 975 if (skb) {
>> 976 if (!net) {
>> 977 if (skb->dev)
>> 978 net = dev_net(skb->dev);
>> 979 else if (skb->sk)
>> 980 net = sock_net(skb->sk);
>> 981 }
>> 982 }
>> 983
>> 984 WARN_ON_ONCE(!net);
>>
>> So, if the skb->hash is not available, then fallback to use 4-tuple derived hash.
>>
>> Fixes: 9466a1ccebbe("mptcp: enable JOIN requests even if cookies are in use").
>> Suggested-by: Paolo Abeni <pabeni@redhat.com>
>> Signed-off-by: Jianguo Wu <wujianguo@chinatelecom.cn>
>> ---
>> net/mptcp/syncookies.c | 24 +++++++++++++++++++++++-
>> 1 file changed, 23 insertions(+), 1 deletion(-)
>>
>> diff --git a/net/mptcp/syncookies.c b/net/mptcp/syncookies.c
>> index abe0fd0..778bdba 100644
>> --- a/net/mptcp/syncookies.c
>> +++ b/net/mptcp/syncookies.c
>> @@ -35,9 +35,31 @@ struct join_entry {
>> static struct join_entry join_entries[COOKIE_JOIN_SLOTS] __cacheline_aligned_in_smp;
>> static spinlock_t join_entry_locks[COOKIE_JOIN_SLOTS] __cacheline_aligned_in_smp;
>>
>> +static u32 mptcp_join_hashfn(const struct net *net, const __be32 laddr,
>> + const __be16 lport, const __be32 faddr,
>> + const __be16 fport)
>> +{
>> + static u32 mptcp_join_hash_secret __read_mostly;
>> +
>> + net_get_random_once(&mptcp_join_hash_secret, sizeof(mptcp_join_hash_secret));
>> +
>> + return jhash_3words((__force __u32) laddr,
>> + (__force __u32) faddr,
>> + ((__u32) lport) << 16 | (__force __u32)fport,
>> + mptcp_join_hash_secret + net_hash_mix(net));
>> +}
>> +
>> static u32 mptcp_join_entry_hash(struct sk_buff *skb, struct net *net)
>> {
>> - u32 i = skb_get_hash(skb) ^ net_hash_mix(net);
>> + u32 i;
>> + struct iphdr *iph = ip_hdr(skb);
>> + struct tcphdr *th = tcp_hdr(skb);
>> +
>> + if (!skb_get_hash_raw(skb))
>> + i = mptcp_join_hashfn(net, iph->daddr, th->dest,
>> + iph->saddr, th->source);
>
> Here we need to handle ipv6 sockets/addresses, too. See sk_ehashfn()
> in net/ipv4/inet_hashtables.c for some reference code.
>
Will add ipv6 handle,thanks.
> There is an additional caveat I haven't thought before: teorically the
> syn and the 3rd ack skbs could be received via different interfaces,
> which will produce different skb->hash value. Or the NIC hash could be
> teorically disabled (or enabled) in between.
>
> TL;DR: I think we should always use the mptcp_join_hashfn() and never
> look at skb->hash.
>
Ok, thanks!
Jianguo
> Sorry for the late feedback,
>
> Paolo
>
^ permalink raw reply [flat|nested] 3+ messages in thread
end of thread, other threads:[~2021-06-10 3:33 UTC | newest]
Thread overview: 3+ messages (download: mbox.gz / follow: Atom feed)
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2021-06-09 10:39 [PATCH 1/3] mptcp: fix warning in __skb_flow_dissect() when do syn cookie for subflow join Jianguo Wu
2021-06-09 14:31 ` Paolo Abeni
2021-06-10 3:18 ` Jianguo Wu
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