Return-Path: Date: Wed, 25 Nov 2015 19:17:17 +0100 From: Alexander Aring To: Stefan Schmidt Cc: linux-wpan@vger.kernel.org, linux-bluetooth@vger.kernel.org, netdev@vger.kernel.org, kernel@pengutronix.de, mcr@sandelman.ca, lukasz.duda@nordicsemi.no, martin.gergeleit@hs-rm.de, "David S . Miller" , Alexey Kuznetsov , James Morris , Hideaki YOSHIFUJI , Patrick McHardy Subject: Re: [RFCv2 bluetooth-next 2/3] ipv6: add ipv6_addr_prefix_cpy Message-ID: <20151125181713.GC4652@omega> References: <1447799594-6050-1-git-send-email-alex.aring@gmail.com> <1447799594-6050-3-git-send-email-alex.aring@gmail.com> <5655E50C.5090906@osg.samsung.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 In-Reply-To: <5655E50C.5090906@osg.samsung.com> Sender: linux-wpan-owner@vger.kernel.org List-ID: On Wed, Nov 25, 2015 at 05:42:52PM +0100, Stefan Schmidt wrote: > Hello. > > On 17/11/15 23:33, Alexander Aring wrote: > >This patch adds a static inline function ipv6_addr_prefix_cpy which > >copies a ipv6 address prefix(argument pfx) into the ipv6 address prefix. > >The prefix len is given by plen as bits. This function mainly based on > >ipv6_addr_prefix which copies one address prefix from address into a new > >ipv6 address destination and zero all other address bits. > > > >The difference is that ipv6_addr_prefix_cpy don't get a prefix from an > >ipv6 address, it sets a prefix to an ipv6 address with keeping other > >address bits. The use case is for context based address compression > >inside 6LoWPAN IPHC header which keeping ipv6 prefixes inside a context > >table to lookup address-bits without sending them. > > > >Cc: David S. Miller > >Cc: Alexey Kuznetsov > >Cc: James Morris > >Cc: Hideaki YOSHIFUJI > >Cc: Patrick McHardy > >Signed-off-by: Alexander Aring > >--- > > include/net/ipv6.h | 15 +++++++++++++++ > > 1 file changed, 15 insertions(+) > > > >diff --git a/include/net/ipv6.h b/include/net/ipv6.h > >index e1a10b0..9d38fc2 100644 > >--- a/include/net/ipv6.h > >+++ b/include/net/ipv6.h > >@@ -382,6 +382,21 @@ static inline void ipv6_addr_prefix(struct in6_addr *pfx, > > pfx->s6_addr[o] = addr->s6_addr[o] & (0xff00 >> b); > > } > >+static inline void ipv6_addr_prefix_cpy(struct in6_addr *addr, > >+ const struct in6_addr *pfx, > >+ int plen) > >+{ > > Naming it ipv6_addr_prefix_cop, as Sergei suggested, would be easier to > read. ok. > >+ /* caller must guarantee 0 <= plen <= 128 */ > >+ int o = plen >> 3, > >+ b = plen & 0x7; > >+ > > Any reason you are not doing the memset here before memcpy like it is done > in ipv6_addr_prefi()? ipv6_addr_prefix is more a "getter" for a prefix from an address. The destination address (which should be the result) will memset the whole address before copy the prefix from address to it. THe ipv6_addr_prefix_copy will set a prefix given by second parameter pfx and set the prefix to the address (given by first parameter). Maybe the ipv6_addr_prefix could call: 1. memset(pfx, sizeof...) 2. ipv6_addr_prefix_copy(pfx, addr, plen); but ipv6_addr_prefix_copy need to care about other bits which are set at destination address, if (plen/8 != 0). I don't want to touch ipv6_addr_prefix function and slow-down some mechanism. - Alex