Re: [U-Boot] [RFC PATCH 4/8] lib: net_utils: add string_to_ip6

Hi Chris,

On Mon, Oct 12, 2015 at 2:43 AM, Chris Packham judge.packham@gmail.com wrote:

string_to_ip6 parses an IPv6 address from a string. Parsing v6 addresses is a bit more complicated than parsing v4 because there are a number of different formats that can be used.

Signed-off-by: Chris Packham judge.packham@gmail.com

I'm sure the parsing can be better and done in less code with only a single pass but I haven't yet figured it out. The main problem is that "::" can represent a variable number of contiguous "0000:" so when parsing "::" we can't tell how many half words to skip.

include/net6.h | 3 ++ lib/net_utils.c | 119 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 2 files changed, 122 insertions(+)

diff --git a/include/net6.h b/include/net6.h index 1b82c25..a41eb87 100644 --- a/include/net6.h +++ b/include/net6.h @@ -58,4 +58,7 @@ static inline int ipv6_addr_is_isatap(const struct in6_addr *a) return (a->s6_addr32[2] | htonl(0x02000000)) == htonl(0x02005EFE); }

+/* Convert a string to an ipv6 address */ +int string_to_ip6(const char *s, struct in6_addr *addr);

#endif /* __NET6_H__ */ diff --git a/lib/net_utils.c b/lib/net_utils.c index 0fca54d..b0d0364 100644 --- a/lib/net_utils.c +++ b/lib/net_utils.c @@ -11,6 +11,8 @@ */

#include <common.h> +#include <net6.h> +#include <linux/ctype.h>

struct in_addr string_to_ip(const char *s) { @@ -43,3 +45,120 @@ struct in_addr string_to_ip(const char *s) addr.s_addr = htonl(addr.s_addr); return addr; }

+/**

• • Parses an struct in6_addr from the given string. IPv6 address parsing is a bit
• • more complicated than v4 due to the flexible format and some of the special
• • cases (e.g. v4 mapped).
• • Examples of valid strings:
• • 2001:db8::0:1234:1
• • 2001:0db8:0000:0000:0000:0000:1234:0001
• • ::1
• • ::ffff:192.168.1.1
• • Examples of invalid strings
• • 2001:db8::0::0 (:: can only appear once)
• • 2001:db8:192.168.1.1::1 (v4 part can only appear at the end)
• • 192.168.1.1 (we don't implicity map v4)
• */

+int string_to_ip6(const char *strpt, struct in6_addr *addrpt) +{

•   int colon_count = 0;
  

•   int found_double_colon = 0;
  

•   int xstart = 0;         /* first zero (double colon) */
  

•   int len = 7;            /* num words the double colon represents */
  

•   int i;
  

•   const char *s = strpt;
  

•   struct in_addr zero_ip = {.s_addr = 0};
  

•   if (strpt == NULL)
  

•           return -1;
  

•   /* First pass, verify the syntax and locate the double colon */
  

•   for (;;) {
  

•           while (isxdigit((int)*s))
  

•                   s++;
  

•           if (*s == '\0')
  

•                   break;
  

•           if (*s != ':') {
  

•                   if (*s == '.' && len >= 2) {
  

•                           struct in_addr v4;
  

•                           while (s != strpt && *(s - 1) != ':')
  

•                                   --s;
  

•                           v4 = string_to_ip(s);
  

•                           if (memcmp(&zero_ip, &v4,
  

•                                      sizeof(struct in_addr) != 0)) {
  

•                                   len -= 2;
  

•                                   break;
  

•                           }
  

•                   }
  

•                   /* This could be a valid address */
  

•                   break;
  

•           }
  

•           if (s == strpt) {
  

•                   /* The address begins with a colon */
  

•                   if (*++s != ':')
  

•                           /* Must start with a double colon or a number */
  

•                           goto out_err;
  

•           } else {
  

•                   s++;
  

•                   if (found_double_colon)
  

•                           len--;
  

•                   else
  

•                           xstart++;
  

•           }
  

•           if (*s == ':') {
  

•                   if (found_double_colon)
  

•                           /* Two double colons are not allowed */
  

•                           goto out_err;
  

•                   found_double_colon = 1;
  

•                   len -= xstart;
  

•                   s++;
  

•           }
  

•           if (++colon_count == 7)
  

•                   /* Found all colons */
  

•                   break;
  

•   }
  

•   if (colon_count == 0 || colon_count > 7)
  

•           goto out_err;
  

Above you bail out if colon_count == 7 so how could it be greater here? My guess is you need to use strchr() to check for additional colons in the remaining string.

•   if (*--s == ':')
  

•           len++;
  

•   /* Second pass, read the address */
  

•   s = strpt;
  

•   for (i = 0; i < 8; i++) {
  

•           int val = 0;
  

•           char *end;
  

•           if (found_double_colon && i >= xstart && i < xstart + len) {
  

•                   addrpt->s6_addr16[i] = 0;
  

•                   continue;
  

•           }
  

•           while (*s == ':')
  

•                   s++;
  

•           if (i == 6 && isdigit((int)*s)) {
  

•                   struct in_addr v4 = string_to_ip(s);
  

•                   if (memcmp(&zero_ip, &v4,
  

•                              sizeof(struct in_addr)) != 0) {
  

•                           /* Ending with :IPv4-address */
  

•                           addrpt->s6_addr32[3] = v4.s_addr;
  

•                           break;
  

•                   }
  

•           }
  

•           val = simple_strtoul(s, &end, 16);
  

•           if (*end != '\0' && *end != ':')
  

•                   goto out_err;
  

•           addrpt->s6_addr16[i] = htons(val);
  

•           s = end;
  

•   }
  

•   return 0;
  

+out_err:

•   return -1;
  

+}

I tend to think we can revisit this to make it more concise in the future. Assuming this is functional, it is better to have a solution even if it's not the perfect solution.

Cheers, -Joe