Date: Fri, 02 Nov 2012 13:54:50 +0100 From: Andre Oppermann <oppermann@networx.ch> To: Gleb Smirnoff <glebius@FreeBSD.org> Cc: net@FreeBSD.org Subject: Re: splitting m_flags to pkthdr.flags + m_flags Message-ID: <5093C29A.4020902@networx.ch> In-Reply-To: <20121102123817.GP70741@FreeBSD.org> References: <20121102123817.GP70741@FreeBSD.org>
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On 02.11.2012 13:38, Gleb Smirnoff wrote: > Hello networkers, > > some (most) of m_flags bits are describing features that can > be present on a packet only, not on a single mbuf. Since we are > close to exhaustion of available bits, and many subsystems prefer > to use one of M_PROTO bits instead of grabbing a flag, I propose The use of M_PROTO for protocol and layer specific use is very much its intended purpose and should be kept that way with overlays. The available range of M_PROTO can be extended with your proposed change. M_PROTO could be split into mbuf and mbuf header flags. Most of the time they are also only relevant on packets. > to split m_flags to two parts: I fully agree on the split. The previous mixing of mbuf and mbuf header flags was irritating and confusing. > In the m_flags remain: > #define M_EXT 0x00000001 /* has associated external storage */ > #define M_PKTHDR 0x00000002 /* start of record */ > #define M_EOR 0x00000004 /* end of record */ > #define M_RDONLY 0x00000008 /* associated data is marked read-only */ > and all M_PROTO flags. > > struct pkthdr grows by one word and its new flag word now > posesses: > > #define M_BCAST 0x00000200 /* send/received as link-level broadcast */ > #define M_MCAST 0x00000400 /* send/received as link-level multicast */ > #define M_FRAG 0x00000800 /* packet is a fragment of a larger packet */ > #define M_FIRSTFRAG 0x00001000 /* packet is first fragment */ > #define M_LASTFRAG 0x00002000 /* packet is last fragment */ I wonder if actually have any users of the M_*FRAG flags. And if yes, if it can be solved in a different way with less flags. > #define M_SKIP_FIREWALL 0x00004000 /* skip firewall processing */ This one should become an M_PROTO overlay. It is only relevant within a protocol layer. > #define M_VLANTAG 0x00010000 /* ether_vtag is valid */ > #define M_PROMISC 0x00020000 /* packet was not for us */ > #define M_FLOWID 0x00400000 /* deprecated: flowid is valid */ > #define M_HASHTYPEBITS 0x0F000000 /* mask of bits holding flowid hash type */ > > Some M_PROTO abusements like M_FASTFWD_OURS and recently added M_IP_NEXTHOP > also go to the pkthdr mbuf flags. On the contrary. This isn't abuse of M_PROTO. It's the exact pupose of it. > P.S. > An attentive reader may have noticed that I missed M_NOFREE and M_FREELIST. > Yep, these flags coming from historical mbuf allocator from FreeBSD 4.x times > are about to be deleted, we carefully examine them, but never set. Patch > for review attached. Looks good. Go ahead from me. -- Andre
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