linux-kernel - Re: [RFC PATCH bpf-next v6 2/3] net: Add additional bit to support clockid

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Date: Tue, 07 May 2024 15:18:22 -0400
From: Willem de Bruijn <willemdebruijn.kernel@...il.com>
To: "Abhishek Chauhan (ABC)" <quic_abchauha@...cinc.com>, 
 Willem de Bruijn <willemdebruijn.kernel@...il.com>, 
 Martin KaFai Lau <martin.lau@...ux.dev>
Cc: "David S. Miller" <davem@...emloft.net>, 
 Eric Dumazet <edumazet@...gle.com>, 
 Jakub Kicinski <kuba@...nel.org>, 
 Paolo Abeni <pabeni@...hat.com>, 
 netdev@...r.kernel.org, 
 linux-kernel@...r.kernel.org, 
 Andrew Halaney <ahalaney@...hat.com>, 
 Martin KaFai Lau <martin.lau@...nel.org>, 
 Daniel Borkmann <daniel@...earbox.net>, 
 bpf <bpf@...r.kernel.org>, 
 kernel@...cinc.com
Subject: Re: [RFC PATCH bpf-next v6 2/3] net: Add additional bit to support
 clockid_t timestamp type

Abhishek Chauhan (ABC) wrote:
> 
> 
> On 5/7/2024 4:39 AM, Willem de Bruijn wrote:
> > Martin KaFai Lau wrote:
> >> On 5/3/24 8:13 PM, Abhishek Chauhan wrote:
> >>> diff --git a/net/ipv4/ip_output.c b/net/ipv4/ip_output.c
> >>> index fe86cadfa85b..c3d852eecb01 100644
> >>> --- a/net/ipv4/ip_output.c
> >>> +++ b/net/ipv4/ip_output.c
> >>> @@ -1457,7 +1457,10 @@ struct sk_buff *__ip_make_skb(struct sock *sk,
> >>>   
> >>>   	skb->priority = (cork->tos != -1) ? cork->priority: READ_ONCE(sk->sk_priority);
> >>>   	skb->mark = cork->mark;
> >>> -	skb->tstamp = cork->transmit_time;
> >>> +	if (sk_is_tcp(sk))
> >>
> >> This seems not catching all IPPROTO_TCP case. In particular, the percpu 
> >> "ipv4_tcp_sk" is SOCK_RAW. sk_is_tcp() is checking SOCK_STREAM:
> >>
> >> void __init tcp_v4_init(void)
> >> {
> >>
> >> 	/* ... */
> >> 	res = inet_ctl_sock_create(&sk, PF_INET, SOCK_RAW,
> >> 				   IPPROTO_TCP, &init_net);
> >>
> >> 	/* ... */
> >> }
> >>
> >> "while :; do ./test_progs -t tc_redirect/tc_redirect_dtime || break; done" 
> >> failed pretty often exactly in this case.
> >>
> > 
> > Interesting. The TCP stack opens non TCP sockets.
> > 
> > Initializing sk->sk_clockid for this socket should address that.
> > 
> Willem, Are you suggesting your point from the previous patch ? 
> 

No, just for this custom socket to initialize the sk_clockid. It is
not a TCP socket, but only used by TCP.