linux-kernel - Re: [PATCH net v3] tcp: check skb is non-NULL in tcp_rto_delta

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Message-ID: <1fbd0d02-6c34-4bb4-b9b8-66e121ff67e3@akamai.com>
Date: Tue, 24 Sep 2024 10:26:17 -0700
From: Josh Hunt <johunt@...mai.com>
To: Paolo Abeni <pabeni@...hat.com>, edumazet@...gle.com, davem@...emloft.net,
        kuba@...nel.org, netdev@...r.kernel.org, ncardwell@...gle.com
Cc: linux-kernel@...r.kernel.org
Subject: Re: [PATCH net v3] tcp: check skb is non-NULL in tcp_rto_delta_us()

On 9/19/24 2:05 AM, Paolo Abeni wrote:
> !-------------------------------------------------------------------|
>   This Message Is From an External Sender
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> 
> On 9/10/24 21:08, Josh Hunt wrote:
>> diff --git a/include/net/tcp.h b/include/net/tcp.h
>> index 2aac11e7e1cc..196c148fce8a 100644
>> --- a/include/net/tcp.h
>> +++ b/include/net/tcp.h
>> @@ -2434,9 +2434,26 @@ static inline s64 tcp_rto_delta_us(const struct 
>> sock *sk)
>>   {
>>       const struct sk_buff *skb = tcp_rtx_queue_head(sk);
>>       u32 rto = inet_csk(sk)->icsk_rto;
>> -    u64 rto_time_stamp_us = tcp_skb_timestamp_us(skb) + 
>> jiffies_to_usecs(rto);
>> -    return rto_time_stamp_us - tcp_sk(sk)->tcp_mstamp;
>> +    if (likely(skb)) {
>> +        u64 rto_time_stamp_us = tcp_skb_timestamp_us(skb) + 
>> jiffies_to_usecs(rto);
>> +
>> +        return rto_time_stamp_us - tcp_sk(sk)->tcp_mstamp;
>> +    } else {
>> +        WARN_ONCE(1,
>> +            "rtx queue emtpy: "
>> +            "out:%u sacked:%u lost:%u retrans:%u "
>> +            "tlp_high_seq:%u sk_state:%u ca_state:%u "
>> +            "advmss:%u mss_cache:%u pmtu:%u\n",
>> +            tcp_sk(sk)->packets_out, tcp_sk(sk)->sacked_out,
>> +            tcp_sk(sk)->lost_out, tcp_sk(sk)->retrans_out,
>> +            tcp_sk(sk)->tlp_high_seq, sk->sk_state,
>> +            inet_csk(sk)->icsk_ca_state,
>> +            tcp_sk(sk)->advmss, tcp_sk(sk)->mss_cache,
>> +            inet_csk(sk)->icsk_pmtu_cookie);
> 
> As the underlying issue here share the same root cause as the one 
> covered by the WARN_ONCE() in tcp_send_loss_probe(), I'm wondering if it 
> would make sense do move the info dumping in a common helper, so that we 
> get the verbose warning on either cases.
> 
> Thanks,
> 
> Paolo

Thanks for the review Paolo. Sorry for the delay in replying I was OOO. 
I can send a follow-up commit to create a common helper.

Josh