Date: Wed, 14 Oct 2015 14:38:59 +0300 From: Gleb Smirnoff <glebius@FreeBSD.org> To: Hiren Panchasara <hiren@FreeBSD.org>, Jonathan Looney <jlooney@juniper.net> Cc: svn-src-head@freebsd.org Subject: Re: svn commit: r289276 - in head/sys: conf kern netinet sys Message-ID: <20151014113859.GS1023@FreeBSD.org> In-Reply-To: <201510140035.t9E0ZbXS030094@repo.freebsd.org> References: <201510140035.t9E0ZbXS030094@repo.freebsd.org>
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Hi, On Wed, Oct 14, 2015 at 12:35:37AM +0000, Hiren Panchasara wrote: H> Author: hiren H> Date: Wed Oct 14 00:35:37 2015 H> New Revision: 289276 H> URL: https://svnweb.freebsd.org/changeset/base/289276 H> H> Log: H> There are times when it would be really nice to have a record of the last few H> packets and/or state transitions from each TCP socket. That would help with H> narrowing down certain problems we see in the field that are hard to reproduce H> without understanding the history of how we got into a certain state. This H> change provides just that. Thanks, Hiren for handling that, and thanks Jonathan for the patch. I have a tiny stylistic suggestion: H> Modified: head/sys/netinet/tcp_var.h H> ============================================================================== H> --- head/sys/netinet/tcp_var.h Wed Oct 14 00:23:31 2015 (r289275) H> +++ head/sys/netinet/tcp_var.h Wed Oct 14 00:35:37 2015 (r289276) H> @@ -37,6 +37,7 @@ H> H> #ifdef _KERNEL H> #include <net/vnet.h> H> +#include <sys/mbuf.h> H> H> /* H> * Kernel variables for tcp. H> @@ -204,7 +205,17 @@ struct tcpcb { H> H> uint32_t t_ispare[8]; /* 5 UTO, 3 TBD */ H> void *t_pspare2[4]; /* 1 TCP_SIGNATURE, 3 TBD */ H> - uint64_t _pad[6]; /* 6 TBD (1-2 CC/RTT?) */ H> +#if defined(_KERNEL) && defined(TCPPCAP) H> + struct mbufq t_inpkts; /* List of saved input packets. */ H> + struct mbufq t_outpkts; /* List of saved output packets. */ H> +#ifdef _LP64 H> + uint64_t _pad[0]; /* all used! */ H> +#else H> + uint64_t _pad[2]; /* 2 are available */ H> +#endif /* _LP64 */ H> +#else H> + uint64_t _pad[6]; H> +#endif /* defined(_KERNEL) && defined(TCPPCAP) */ H> }; What if we write it down this way (thanks C11): struct tcpcb { ... union { #ifdef TCPPCAP struct { struct mbufq t_inpkts; struct mbufq t_outpkts; }; #endif uint64_t _pad[6]; } }; So, compiler cares about pointer size, not us. And more readable, IMHO. -- Totus tuus, Glebius.
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