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

From: Paolo Abeni
Date: Thu Sep 19 2024 - 05:06:08 EST


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