Date: Thu, 14 Mar 2024 11:34:23 -0600 From: Warner Losh <imp@bsdimp.com> To: John Baldwin <jhb@freebsd.org> Cc: Gleb Smirnoff <glebius@freebsd.org>, Konstantin Belousov <kib@freebsd.org>, src-committers@freebsd.org, dev-commits-src-all@freebsd.org, dev-commits-src-main@freebsd.org Subject: Re: git: 220ee18f1964 - main - netinet/tcp_var.h: always define IS_FASTOPEN() for kernel compilation env Message-ID: <CANCZdfp_f%2B1wA4FHEY_CL%2BPBcCcP2u2mezrgvno%2B=c%2B2DGJQcA@mail.gmail.com> In-Reply-To: <56f538f1-d406-4095-972a-2022d48ffc73@FreeBSD.org> References: <202403132321.42DNLNIX087785@gitrepo.freebsd.org> <ZfJDsRPzASbZ_Cav@cell.glebi.us> <56f538f1-d406-4095-972a-2022d48ffc73@FreeBSD.org>
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[-- Attachment #1 --] On Thu, Mar 14, 2024 at 11:23 AM John Baldwin <jhb@freebsd.org> wrote: > On 3/13/24 5:24 PM, Gleb Smirnoff wrote: > > On Wed, Mar 13, 2024 at 11:21:23PM +0000, Konstantin Belousov wrote: > > K> diff --git a/sys/netinet/tcp_var.h b/sys/netinet/tcp_var.h > > K> index 6f7f7115c2f4..7b5c57d39213 100644 > > K> --- a/sys/netinet/tcp_var.h > > K> +++ b/sys/netinet/tcp_var.h > > K> @@ -812,11 +812,13 @@ tcp_packets_this_ack(struct tcpcb *tp, tcp_seq > ack) > > K> #define ENTER_RECOVERY(t_flags) t_flags |= (TF_CONGRECOVERY | > TF_FASTRECOVERY) > > K> #define EXIT_RECOVERY(t_flags) t_flags &= ~(TF_CONGRECOVERY | > TF_FASTRECOVERY) > > K> > > K> -#if defined(_KERNEL) && !defined(TCP_RFC7413) > > K> +#if defined(_KERNEL) > > K> +#if !defined(TCP_RFC7413) > > K> #define IS_FASTOPEN(t_flags) (false) > > K> #else > > K> #define IS_FASTOPEN(t_flags) (t_flags & TF_FASTOPEN) > > K> #endif > > K> +#endif > > K> > > K> #define BYTES_THIS_ACK(tp, th) (th->th_ack - tp->snd_una) > > > > I know Konstantin in doing that to clear path for IPSEC changes, and the > patch > > does improve code. So the message isn't addressed to him, rather it is > for > > other src-committers. > > > > Using ifdefs that come from the kernel config inside include files that > are not > > ephemeral opt_foo.h is laying out a minefield for the future. Best case > - for > > yourself, worst case - for somebody else. > > +100 > +100 as well. I can't tell you how many times I've been burned by this, had to mop up for it after the fact, etc over the years. > > In the best case this ends in cryptic kernel failure builds, where your > custom > > kernel doesn't build, but GENERIC builds and it is not clear why. In the > worst > > case this creates runtime failures even more cryptic in their nature. > > > > In this particular case TCP_RFC7413 comes via opt_inet.h. Thus, if you > got a > > userland tool, e.g. netstat(1) using IS_FASTOPEN() it will always be > false. > > Again, netstat would be a best case. A worst case would be netinet6 > kernel > > compilation unit that does not include opt_inet.h, but uses > IS_FASTOPEN(). > > > > Other than that, we got 32 flags for t_flags and only one is obfuscated > via a > > macro. I'd really like to remove the macro and test the flag directly. > Any > > objections? > > +1 > Yea, this macro isn't that special, and there's no good reason from looking at the code it should get such special treatment. Warner [-- Attachment #2 --] <div dir="ltr"><div dir="ltr"><br></div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Thu, Mar 14, 2024 at 11:23 AM John Baldwin <<a href="mailto:jhb@freebsd.org">jhb@freebsd.org</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">On 3/13/24 5:24 PM, Gleb Smirnoff wrote:<br> > On Wed, Mar 13, 2024 at 11:21:23PM +0000, Konstantin Belousov wrote:<br> > K> diff --git a/sys/netinet/tcp_var.h b/sys/netinet/tcp_var.h<br> > K> index 6f7f7115c2f4..7b5c57d39213 100644<br> > K> --- a/sys/netinet/tcp_var.h<br> > K> +++ b/sys/netinet/tcp_var.h<br> > K> @@ -812,11 +812,13 @@ tcp_packets_this_ack(struct tcpcb *tp, tcp_seq ack)<br> > K> #define ENTER_RECOVERY(t_flags) t_flags |= (TF_CONGRECOVERY | TF_FASTRECOVERY)<br> > K> #define EXIT_RECOVERY(t_flags) t_flags &= ~(TF_CONGRECOVERY | TF_FASTRECOVERY)<br> > K><br> > K> -#if defined(_KERNEL) && !defined(TCP_RFC7413)<br> > K> +#if defined(_KERNEL)<br> > K> +#if !defined(TCP_RFC7413)<br> > K> #define IS_FASTOPEN(t_flags) (false)<br> > K> #else<br> > K> #define IS_FASTOPEN(t_flags) (t_flags & TF_FASTOPEN)<br> > K> #endif<br> > K> +#endif<br> > K><br> > K> #define BYTES_THIS_ACK(tp, th) (th->th_ack - tp->snd_una)<br> > <br> > I know Konstantin in doing that to clear path for IPSEC changes, and the patch<br> > does improve code. So the message isn't addressed to him, rather it is for<br> > other src-committers.<br> > <br> > Using ifdefs that come from the kernel config inside include files that are not<br> > ephemeral opt_foo.h is laying out a minefield for the future. Best case - for<br> > yourself, worst case - for somebody else.<br> <br> +100<br></blockquote><div><br></div><div>+100 as well. I can't tell you how many times I've been burned by this, had to mop</div><div>up for it after the fact, etc over the years.</div><div> </div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"> > In the best case this ends in cryptic kernel failure builds, where your custom<br> > kernel doesn't build, but GENERIC builds and it is not clear why. In the worst<br> > case this creates runtime failures even more cryptic in their nature.<br> > <br> > In this particular case TCP_RFC7413 comes via opt_inet.h. Thus, if you got a<br> > userland tool, e.g. netstat(1) using IS_FASTOPEN() it will always be false.<br> > Again, netstat would be a best case. A worst case would be netinet6 kernel<br> > compilation unit that does not include opt_inet.h, but uses IS_FASTOPEN().<br> > <br> > Other than that, we got 32 flags for t_flags and only one is obfuscated via a<br> > macro. I'd really like to remove the macro and test the flag directly. Any<br> > objections?<br> <br> +1<br></blockquote><div><br></div><div>Yea, this macro isn't that special, and there's no good reason from looking at</div><div>the code it should get such special treatment.</div><div><br></div><div>Warner</div></div></div>help
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