From mboxrd@z Thu Jan 1 00:00:00 1970 From: Brian Haley Subject: Re: [RFC] ipv6: Change %pI6 format to output compacted addresses? Date: Thu, 13 Aug 2009 12:27:35 -0400 Message-ID: <4A843EF7.4010700@hp.com> References: <1250091560.6641.48.camel@fnki-nb00130> <4A836D6D.1040400@hp.com> <1250174390.6641.89.camel@fnki-nb00130> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Cc: Linux Network Developers To: Jens Rosenboom Return-path: Received: from g1t0028.austin.hp.com ([15.216.28.35]:22873 "EHLO g1t0028.austin.hp.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751569AbZHMQ1r (ORCPT ); Thu, 13 Aug 2009 12:27:47 -0400 In-Reply-To: <1250174390.6641.89.camel@fnki-nb00130> Sender: netdev-owner@vger.kernel.org List-ID: Jens Rosenboom wrote: >> Anyways, can you try this patch, it's less than 40 new lines :) >> It might be good enough, but could probably use some help. > > For a start, it didn't even compile. ;-) It did on net-next-2.6 last night, weird. > Here is a new version that also > fixes > > - Leave %pi6 alone > - Don't compress a single :0: > - Do output 0 > > The results and also the remaining issues can be seen with the attached > test program, that also exposes a bug in glibc for v4-mapped addresses > from 0/16. > > To fully conform to the cited draft, we would still have to implement > v4-mapped and also check whether a second run of zeros would be longer > than the first one, although the draft also suggests that operators > should avoid using this kind of addresses, so maybe this second issue > can be neglected. Yes, the "compress the most zeros" would be harder, and require two passes over the address. I had to cut corners somewhere :) And regarding v4-mapped, the easy fix to that is just detect it and call the IPv4 routine. The attached patch does that, but without the ::ffff: > diff --git a/lib/vsprintf.c b/lib/vsprintf.c > index 756ccaf..5710c65 100644 > --- a/lib/vsprintf.c > +++ b/lib/vsprintf.c > @@ -652,13 +652,53 @@ static char *ip6_addr_string(char *buf, char *end, > u8 *addr, > { > char ip6_addr[8 * 5]; /* (8 * 4 hex digits), 7 colons and trailing > zero */ > char *p = ip6_addr; > - int i; > + int i, needcolon = 0, printhi; > + u16 *addr16 = (u16 *)addr; > + enum { DC_START, DC_MIDDLE, DC_DONE } colon = DC_START; > + > + /* omit leading zeros and shorten using "::" */ > > - for (i = 0; i < 8; i++) { > - p = pack_hex_byte(p, addr[2 * i]); > - p = pack_hex_byte(p, addr[2 * i + 1]); > - if (!(spec.flags & SPECIAL) && i != 7) > + if (!(spec.flags & SPECIAL)) { > + for (i = 0; i < 8; i++) { > + if (addr16[i] == 0 && addr16[i+1] == 0 && colon == DC_START) { This will access the array out-of-bounds when i=7. Another hack below. -Brian diff --git a/lib/vsprintf.c b/lib/vsprintf.c index 756ccaf..ba70f2a 100644 --- a/lib/vsprintf.c +++ b/lib/vsprintf.c @@ -647,25 +647,6 @@ static char *mac_address_string(char *buf, char *end, u8 *addr, return string(buf, end, mac_addr, spec); } -static char *ip6_addr_string(char *buf, char *end, u8 *addr, - struct printf_spec spec) -{ - char ip6_addr[8 * 5]; /* (8 * 4 hex digits), 7 colons and trailing zero */ - char *p = ip6_addr; - int i; - - for (i = 0; i < 8; i++) { - p = pack_hex_byte(p, addr[2 * i]); - p = pack_hex_byte(p, addr[2 * i + 1]); - if (!(spec.flags & SPECIAL) && i != 7) - *p++ = ':'; - } - *p = '\0'; - spec.flags &= ~SPECIAL; - - return string(buf, end, ip6_addr, spec); -} - static char *ip4_addr_string(char *buf, char *end, u8 *addr, struct printf_spec spec) { @@ -688,6 +669,73 @@ static char *ip4_addr_string(char *buf, char *end, u8 *addr, return string(buf, end, ip4_addr, spec); } +static char *ip6_addr_string(char *buf, char *end, u8 *addr, + struct printf_spec spec) +{ + char ip6_addr[8 * 5]; /* (8 * 4 hex digits), 7 colons and trailing zero */ + char *p = ip6_addr; + int i, needcolon, printhi; + u16 *addr16 = (u16 *)addr; + u32 *addr32 = (u32 *)addr; + enum { DC_START, DC_MIDDLE, DC_DONE } colon = DC_START; + + if (!(spec.flags & SPECIAL)) { + /* omit leading zeros and shorten using "::" */ + + /* v4mapped */ + if ((addr32[0] | addr32[1] | + (addr32[2] ^ htonl(0x0000ffff))) == 0) + return ip4_addr_string(buf, end, &addr[12], spec); + + needcolon = 0; + for (i = 0; i < 8; i++) { + if (addr16[i] == 0 && i < 7 && addr16[i+1] == 0 && + colon == DC_START) { + colon = DC_MIDDLE; + continue; + } + if (colon == DC_MIDDLE) { + if (addr16[i] == 0) + continue; + colon = DC_DONE; + *p++ = ':'; + *p++ = ':'; + } else if (needcolon) + *p++ = ':'; + printhi = 0; + if (addr[2 * i]) { + if (addr[2 * i] > 0x0f) + p = pack_hex_byte(p, addr[2 * i]); + else + *p++ = hex_asc_lo(addr[2 * i]); + printhi++; + } + /* + * If we printed the high-order bits we must print the + * low-order ones, even if they're all zeros. + */ + if (printhi || addr[2 * i + 1] > 0x0f) + p = pack_hex_byte(p, addr[2 * i + 1]); + else + *p++ = hex_asc_lo(addr[2 * i + 1]); + needcolon++; + } + if (colon == DC_MIDDLE) { + *p++ = ':'; + *p++ = ':'; + } + } else { + for (i = 0; i < 8; i++) { + p = pack_hex_byte(p, addr[2 * i]); + p = pack_hex_byte(p, addr[2 * i + 1]); + } + } + *p = '\0'; + spec.flags &= ~SPECIAL; + + return string(buf, end, ip6_addr, spec); +} + /* * Show a '%p' thing. A kernel extension is that the '%p' is followed * by an extra set of alphanumeric characters that are extended format