Re: [RFC] ipv6: Change %pI6 format to output compacted addresses?
From: Joe Perches <joe@perches.com>
Date: 2009-08-13 18:10:39
Subsystem:
library code, the rest, vsprintf · Maintainers:
Andrew Morton, Linus Torvalds, Petr Mladek, Steven Rostedt
On Thu, 2009-08-13 at 12:27 -0400, Brian Haley wrote:
Jens Rosenboom wrote:quoted
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 :)
2 things. First a question, then a compilable but untested patch. The patch allows "%p6ic" for compressed and "%p6ic4" for compressed with ipv4 last u32. Can somebody tell me what I'm doing wrong when I link Jens' test? cc -o test test_ipv6.c lib/vsprintf.o lib/ctype.o lib/vsprintf.o: In function `global constructors keyed to 65535_0_simple_strtoul': /home/joe/linux/linux-2.6/lib/vsprintf.c:1972: undefined reference to `__gcov_init' lib/vsprintf.o:(.data+0x28): undefined reference to `__gcov_merge_add' collect2: ld returned 1 exit status Now for the patch. Perhaps something like this (compiled, untested)
diff --git a/lib/vsprintf.c b/lib/vsprintf.c
index 756ccaf..dd02842 100644
--- a/lib/vsprintf.c
+++ b/lib/vsprintf.c@@ -630,7 +630,7 @@ static char *resource_string(char *buf, char *end, struct resource *res, } static char *mac_address_string(char *buf, char *end, u8 *addr, - struct printf_spec spec) + struct printf_spec spec, const char *fmt) { char mac_addr[6 * 3]; /* (6 * 2 hex digits), 5 colons and trailing zero */ char *p = mac_addr;
@@ -638,36 +638,128 @@ static char *mac_address_string(char *buf, char *end, u8 *addr, for (i = 0; i < 6; i++) { p = pack_hex_byte(p, addr[i]); - if (!(spec.flags & SPECIAL) && i != 5) + if (!(fmt[0] == 'm') && i != 5) *p++ = ':'; } *p = '\0'; - spec.flags &= ~SPECIAL; return string(buf, end, mac_addr, spec); } +typedef enum { DC_START, DC_MIDDLE, DC_DONE } ip6_colon_t; + +static char *ip6_compress_u16(char *p, u16 addr16, u16 addr16_next, + ip6_colon_t *colon, bool *needcolon) +{ + bool printhi; + u8 hi; + u8 lo; + + if (addr16 == 0 && addr16_next == 0 && *colon == DC_START) { + *colon = DC_MIDDLE; + return p; + } + if (*colon == DC_MIDDLE) { + if (addr16 == 0) + return p; + *colon = DC_DONE; + *p++ = ':'; + *p++ = ':'; + } else if (*needcolon) + *p++ = ':'; + + printhi = false; + hi = addr16 >> 8; + lo = addr16 & 0xff; + if (hi) { + if (hi > 0x0f) + p = pack_hex_byte(p, hi); + else + *p++ = hex_asc_lo(hi); + printhi = true; + } + /* + * If we printed the high-order bits we must print the + * low-order ones, even if they're all zeros. + */ + if (printhi || lo > 0x0f) + p = pack_hex_byte(p, lo); + else + *p++ = hex_asc_lo(lo); + *needcolon = true; + + return p; +} + +static char *ip6_compressed_string(char *buf, char *end, u8 *addr, + struct printf_spec spec, const char *fmt, + char *ip6_addr) +{ + char *p = ip6_addr; + int i; + bool needcolon = false; + u16 *addr16 = (u16 *)addr; + ip6_colon_t colon = DC_START; + + if (fmt[3] == '4') { /* use :: and ipv4 */ + for (i = 0; i < 6; i++) { + p = ip6_compress_u16(p, addr16[i], addr16[i+1], + &colon, &needcolon); + } + if (colon != DC_DONE) { + *p++ = ':'; + *p++ = ':'; + colon = DC_DONE; + } + addr += 6 * 2; + for (i = 0; i < 4; i++) { + p = put_dec_trunc(p, *addr++); + if (i != 3) + *p++ = '.'; + } + } else { + for (i = 0; i < 7; i++) { + p = ip6_compress_u16(p, addr16[i], addr16[i+1], + &colon, &needcolon); + } + p = ip6_compress_u16(p, addr16[7], 0xff, &colon, &needcolon); + } + + if (colon == DC_MIDDLE) { + *p++ = ':'; + *p++ = ':'; + } + + *p = '\0'; + + return string(buf, end, ip6_addr, spec); +} + static char *ip6_addr_string(char *buf, char *end, u8 *addr, - struct printf_spec spec) + struct printf_spec spec, const char *fmt) { - char ip6_addr[8 * 5]; /* (8 * 4 hex digits), 7 colons and trailing zero */ + char ip6_addr[7 * 4 + 7 + 4 * 4]; /* (7 * 4 hex digits) + 7 colons + + * ipv4 address, and trailing zero */ char *p = ip6_addr; int i; + if (fmt[0] == 'i' && fmt[2] == 'c') + return ip6_compressed_string(buf, end, addr, spec, fmt, + ip6_addr); + 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 (fmt[0] == 'i' && 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) + struct printf_spec spec) { char ip4_addr[4 * 4]; /* (4 * 3 decimal digits), 3 dots and trailing zero */ char temp[3]; /* hold each IP quad in reverse order */
@@ -683,11 +775,18 @@ static char *ip4_addr_string(char *buf, char *end, u8 *addr, *p++ = '.'; } *p = '\0'; - spec.flags &= ~SPECIAL; return string(buf, end, ip4_addr, spec); } +static char *ip_addr_string(char *buf, char *end, u8 *addr, + struct printf_spec spec, const char *fmt) +{ + if (fmt[1] == '6') + return ip6_addr_string(buf, end, addr, spec, fmt); + return ip4_addr_string(buf, end, 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
@@ -726,20 +825,19 @@ static char *pointer(const char *fmt, char *buf, char *end, void *ptr, return symbol_string(buf, end, ptr, spec, *fmt); case 'R': return resource_string(buf, end, ptr, spec); - case 'm': - spec.flags |= SPECIAL; - /* Fallthrough */ - case 'M': - return mac_address_string(buf, end, ptr, spec); - case 'i': - spec.flags |= SPECIAL; - /* Fallthrough */ - case 'I': - if (fmt[1] == '6') - return ip6_addr_string(buf, end, ptr, spec); - if (fmt[1] == '4') - return ip4_addr_string(buf, end, ptr, spec); - spec.flags &= ~SPECIAL; + case 'm': /* Colon separated: 00:01:02:03:04:05 */ + case 'M': /* Contiguous: 000102030405 */ + return mac_address_string(buf, end, ptr, spec, fmt); + case 'i': /* + * Formatted IP supported + * 4: 001.002.003.004 + * 6: 0001:0203:...:0708 + * 6c: 1::708 + * 6c4: 1::1.2.3.4 + */ + case 'I': /* Contiguous: */ + if (fmt[1] == '4' || fmt[1] == '6') + ip_addr_string(buf, end, ptr, spec, fmt); break; } spec.flags |= SMALL;