Re: [PATCH net v3] tcp: check skb is non-NULL in tcp_rto_delta_us()

[Paolo Abeni <pabeni@redhat.com>]

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