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Date: Thu, 27 Feb 2014 12:39:01 +0000 From: Paul Durrant <Paul.Durrant@...rix.com> To: Jan Beulich <JBeulich@...e.com> CC: "davem@...emloft.net" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, "netdev@...r.kernel.org" <netdev@...r.kernel.org> Subject: RE: [PATCH net-next] consolidate duplicate code is skb_checksum_setup() helpers > -----Original Message----- > From: Jan Beulich [mailto:JBeulich@...e.com] > Sent: 27 February 2014 12:20 > To: Paul Durrant > Cc: davem@...emloft.net; Eric Dumazet; netdev@...r.kernel.org > Subject: RE: [PATCH net-next] consolidate duplicate code is > skb_checksum_setup() helpers > > >>> On 27.02.14 at 13:00, Paul Durrant <Paul.Durrant@...rix.com> wrote: > >> -----Original Message----- > >> From: Jan Beulich [mailto:JBeulich@...e.com] > >> Sent: 27 February 2014 11:50 > >> To: Paul Durrant > >> Cc: davem@...emloft.net; Eric Dumazet; netdev@...r.kernel.org > >> Subject: RE: [PATCH net-next] consolidate duplicate code is > >> skb_checksum_setup() helpers > >> > >> >>> On 27.02.14 at 11:57, Paul Durrant <Paul.Durrant@...rix.com> wrote: > >> >> -----Original Message----- > >> >> From: Jan Beulich [mailto:JBeulich@...e.com] > >> >> Sent: 27 February 2014 09:05 > >> >> To: netdev@...r.kernel.org > >> >> Cc: Paul Durrant; davem@...emloft.net; Eric Dumazet > >> >> Subject: [PATCH net-next] consolidate duplicate code is > >> >> skb_checksum_setup() helpers > >> >> > >> >> Realizing that the skb_maybe_pull_tail() calls in the IP-protocol > >> >> specific portions of both helpers are terminal ones (i.e. no further > >> >> pulls are expected), their maximum size to be pulled can be made > match > >> >> their minimal size needed, thus making the code identical and hence > >> >> possible to be moved into another helper. > >> > > >> > There is a difference in the case of an IPv4 TCP packet with options. > With > >> > your patch it will only get pulled up as far as the base header so there > may > >> > need to be another pull for options parsing. > >> > >> Don't the options start right after the IP header, before the TCP > >> or UDP one? In which case the pull covers them. > >> > > > > *IP* options do, TCP options are immediately after the TCP header (hence > the > > TCP header length field). UDP doesn't have options. > > Oh, right, of course. But then again - is the maximum length of > TCP options different between v4 and v6? If not, that limit > should be used here rather than the more generic (and version > dependent) IP limit. I don't know off the top of my head - I'd have to go look. My hunch is that TCP options are essentially independent of IP version. Anyway, the header is limited to 60 bytes max due to the 4 bit width of the header length field so you may as well just use that. > > And iiuc the UDP case could remain as is. > Yep. Paul -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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