From 285a7fdd2151672ba3d60914848c2113d4ed9d15 Mon Sep 17 00:00:00 2001 From: Florian Obser Date: Thu, 14 Jan 2021 19:15:30 +0100 Subject: [PATCH] Implement IPv4-Embedded addresses according to RFC6052. The original algorithm assumed that any prefix length would be valid and did not skip over bits 64 to 71 and set them to zero. This means that only dns64 prefixes with length 32 and 96 generated embedded addresses according to RFC6052, cf. Figure 1 in 2.2. --- dns64/dns64.c | 40 ++++++++++++++++++++++------------------ 1 file changed, 22 insertions(+), 18 deletions(-) diff --git a/dns64/dns64.c b/dns64/dns64.c index 5c70119a5..e7552bb7d 100644 --- a/dns64/dns64.c +++ b/dns64/dns64.c @@ -198,14 +198,17 @@ uitoa(unsigned n, char* s) static uint32_t extract_ipv4(const uint8_t ipv6[], size_t ipv6_len, const int offset) { - uint32_t ipv4; + uint32_t ipv4 = 0; + int i, pos; log_assert(ipv6_len == 16); (void)ipv6_len; - ipv4 = (uint32_t)ipv6[offset/8+0] << (24 + (offset%8)) - | (uint32_t)ipv6[offset/8+1] << (16 + (offset%8)) - | (uint32_t)ipv6[offset/8+2] << ( 8 + (offset%8)) - | (uint32_t)ipv6[offset/8+3] << ( 0 + (offset%8)); - if (offset/8+4 < 16) - ipv4 |= (uint32_t)ipv6[offset/8+4] >> (8 - offset%8); + log_assert(offset == 32 || offset == 40 || offset == 48 || offset == 56 || + offset == 64 || offset == 96); + for(i = 0, pos = offset / 8; i < 4; i++, pos++) { + if (pos == 8) + pos++; + ipv4 = ipv4 << 8; + ipv4 |= ipv6[pos]; + } return ipv4; } @@ -297,17 +300,16 @@ synthesize_aaaa(const uint8_t prefix_addr[], size_t prefix_addr_len, size_t aaaa_len) { log_assert(prefix_addr_len == 16 && a_len == 4 && aaaa_len == 16); + log_assert(prefix_net == 32 || prefix_net == 40 || prefix_net == 48 || + prefix_net == 56 || prefix_net == 64 || prefix_net == 96); + int i, pos; (void)prefix_addr_len; (void)a_len; (void)aaaa_len; memcpy(aaaa, prefix_addr, 16); - aaaa[prefix_net/8+0] |= a[0] >> (0+prefix_net%8); - aaaa[prefix_net/8+1] |= a[0] << (8-prefix_net%8); - aaaa[prefix_net/8+1] |= a[1] >> (0+prefix_net%8); - aaaa[prefix_net/8+2] |= a[1] << (8-prefix_net%8); - aaaa[prefix_net/8+2] |= a[2] >> (0+prefix_net%8); - aaaa[prefix_net/8+3] |= a[2] << (8-prefix_net%8); - aaaa[prefix_net/8+3] |= a[3] >> (0+prefix_net%8); - if (prefix_net/8+4 < 16) /* <-- my beautiful symmetry is destroyed! */ - aaaa[prefix_net/8+4] |= a[3] << (8-prefix_net%8); + for(i = 0, pos = prefix_net / 8; i < a_len; i++, pos++) { + if(pos == 8) + aaaa[pos++] = 0; + aaaa[pos] = a[i]; + } } @@ -374,8 +376,10 @@ dns64_apply_cfg(struct dns64_env* dns64_env, struct config_file* cfg) log_err("dns64_prefix is not IPv6: %s", cfg->dns64_prefix); return 0; } - if (dns64_env->prefix_net < 0 || dns64_env->prefix_net > 96) { - log_err("dns64-prefix length it not between 0 and 96: %s", + if (dns64_env->prefix_net != 32 && dns64_env->prefix_net != 40 && + dns64_env->prefix_net != 48 && dns64_env->prefix_net != 56 && + dns64_env->prefix_net != 64 && dns64_env->prefix_net != 96 ) { + log_err("dns64-prefix length it not 32, 40, 48, 56, 64 or 96: %s", cfg->dns64_prefix); return 0; } -- 2.47.2