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

[Chris Packham]

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 at 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;
+	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;
+}
-- 
2.5.3