> diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
> index 81ef53f..42bff22 100644
> --- a/include/linux/skbuff.h
> +++ b/include/linux/skbuff.h
> @@ -3300,8 +3300,7 @@ void skb_tstamp_tx(struct sk_buff *orig_skb,
>
> static inline void sw_tx_timestamp(struct sk_buff *skb)
> {
> - if (skb_shinfo(skb)->tx_flags & SKBTX_SW_TSTAMP &&
> - !(skb_shinfo(skb)->tx_flags & SKBTX_IN_PROGRESS))
> + if (skb_shinfo(skb)->tx_flags & SKBTX_SW_TSTAMP)
> skb_tstamp_tx(skb, NULL);
> }
>
> diff --git a/include/uapi/linux/net_tstamp.h b/include/uapi/linux/net_tstamp.h
> index 8fcae35..d251972 100644
> --- a/include/uapi/linux/net_tstamp.h
> +++ b/include/uapi/linux/net_tstamp.h
> @@ -27,8 +27,9 @@ enum {
> SOF_TIMESTAMPING_OPT_TSONLY = (1<<11),
> SOF_TIMESTAMPING_OPT_STATS = (1<<12),
> SOF_TIMESTAMPING_OPT_PKTINFO = (1<<13),
> + SOF_TIMESTAMPING_OPT_TX_SWHW = (1<<14),
>
> - SOF_TIMESTAMPING_LAST = SOF_TIMESTAMPING_OPT_PKTINFO,
> + SOF_TIMESTAMPING_LAST = SOF_TIMESTAMPING_OPT_TX_SWHW,
> SOF_TIMESTAMPING_MASK = (SOF_TIMESTAMPING_LAST - 1) |
> SOF_TIMESTAMPING_LAST
> };
> diff --git a/net/core/skbuff.c b/net/core/skbuff.c
> index 58604c1..db5aa19 100644
> --- a/net/core/skbuff.c
> +++ b/net/core/skbuff.c
> @@ -3874,6 +3874,10 @@ void __skb_tstamp_tx(struct sk_buff *orig_skb,
> if (!sk)
> return;
>
> + if (!hwtstamps && !(sk->sk_tsflags & SOF_TIMESTAMPING_OPT_TX_SWHW) &&
> + skb_shinfo(orig_skb)->tx_flags & SKBTX_IN_PROGRESS)
> + return;
> +
This check should only happen for software transmit timestamps, so simpler to
revise the check in sw_tx_timestamp above to
if (skb_shinfo(skb)->tx_flags & SKBTX_SW_TSTAMP &&
- !(skb_shinfo(skb)->tx_flags & SKBTX_IN_PROGRESS))
+ (!(skb_shinfo(orig_skb)->tx_flags & SKBTX_IN_PROGRESS)) ||
+ (skb->sk && skb->sk->sk_tsflags & SOF_TIMESTAMPING_OPT_TX_SWHW)
> diff --git a/net/socket.c b/net/socket.c
> index 68b9304..14b7688 100644
> --- a/net/socket.c
> +++ b/net/socket.c
> @@ -720,6 +720,7 @@ void __sock_recv_timestamp(struct msghdr *msg, struct
> sock *sk,
> empty = 0;
> if (shhwtstamps &&
> (sk->sk_tsflags & SOF_TIMESTAMPING_RAW_HARDWARE) &&
> + (empty || !skb_is_err_queue(skb)) &&
> ktime_to_timespec_cond(shhwtstamps->hwtstamp, tss.ts + 2)) {
I find skb->tstamp == 0 easier to understand than the condition on empty.
Indeed, this is so non-obvious that I would suggest another helper function
skb_is_hwtx_tstamp with a concise comment about the race condition
between tx software and hardware timestamps (as in the last sentence of
the commit message).
