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Message-Id: <1250187034.28285.93.camel@Joe-Laptop.home>
Date: Thu, 13 Aug 2009 11:10:34 -0700
From: Joe Perches <joe@...ches.com>
To: Brian Haley <brian.haley@...com>
Cc: Jens Rosenboom <jens@...one.net>,
Linux Network Developers <netdev@...r.kernel.org>,
Chuck Lever <chuck.lever@...cle.com>
Subject: Re: [RFC] ipv6: Change %pI6 format to output compacted addresses?
On Thu, 2009-08-13 at 12:27 -0400, Brian Haley wrote:
> Jens Rosenboom wrote:
> > 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;
--
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