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author | Erik Kline <ek@google.com> | 2014-09-22 13:32:27 +0900 |
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committer | Erik Kline <ek@google.com> | 2014-09-24 11:47:10 +0900 |
commit | 89f49ae6d7ddde7a765cce7ecd5006ecf97e8754 (patch) | |
tree | dcc0adda2d2f0abd56f8d562a6198ce53969a039 | |
parent | 05ff508a793c2113ca2a06942f0cec1aec220799 (diff) | |
download | platform_external_android-clat-l-preview.tar.gz platform_external_android-clat-l-preview.tar.bz2 platform_external_android-clat-l-preview.zip |
Simplify and always retry DNS64 prefix discovery.android-l-preview_r2l-preview
- Only request AAAAs for the IPv4-only hostname, since that's
all the information being used. Perhaps at some point in the
future when _validation_ of the IPv4 address(es)'s presence
within the IPv6 address(es) is being done this should be
revisited.
- Only use the first AAAA returned to find the DNS64 prefix.
It's not clear how to properly resolve any potential DNS64
prefix conflicts anyway.
- Re-try DNS64 prefix discovery on any type of error.
If clatd was started (presumably an IPv6-only network), retry
DNS64 prefix discovery with exponential backoff. Some
"permanent" errors can be indistinguishable from transient
errors (e.g. receiving an erroneous SERVFAIL from a DNS
resolver, ...).
- Fix-up back-off logic to not sleep 128 then 120, 120, ...
:-)
Bug: 17569702
Change-Id: I226ea7772cd7c88d2b60153ef76e5435400e11aa
-rw-r--r-- | config.c | 9 | ||||
-rw-r--r-- | dns64.c | 69 |
2 files changed, 24 insertions, 54 deletions
@@ -165,16 +165,11 @@ void dns64_detection(unsigned net_id) { memcpy(&Global_Clatd_Config.plat_subnet, &tmp_ptr, sizeof(struct in6_addr)); return; } - if(status < 0) { - logmsg(ANDROID_LOG_FATAL, "dns64_detection/no dns64, giving up\n"); - exit(1); - } - logmsg(ANDROID_LOG_WARN, "dns64_detection failed, sleeping for %d seconds", backoff_sleep); + logmsg(ANDROID_LOG_WARN, "dns64_detection -- error, sleeping for %d seconds", backoff_sleep); sleep(backoff_sleep); + backoff_sleep *= 2; if(backoff_sleep >= 120) { backoff_sleep = 120; - } else { - backoff_sleep *= 2; } } } @@ -30,69 +30,44 @@ #include "resolv_netid.h" /* function: plat_prefix - * looks up an ipv4-only hostname and looks for a nat64 /96 prefix, returns 1 on success, 0 on temporary failure, -1 on permanent failure + * looks up an ipv4-only hostname and looks for a nat64 /96 prefix, returns 1 on success, 0 on failure * ipv4_name - name to lookup * net_id - (optional) netId to use, NETID_UNSET indicates use of default network * prefix - the plat /96 prefix */ int plat_prefix(const char *ipv4_name, unsigned net_id, struct in6_addr *prefix) { - struct addrinfo hints, *result, *p; - int status, plat_addr_set, ipv4_records, ipv6_records; - struct in6_addr plat_addr, this_plat_addr; - struct sockaddr_in6 *this_addr; + const struct addrinfo hints = { + .ai_family = AF_INET6, + }; + int status; + struct addrinfo *result = NULL; + struct in6_addr plat_addr; char plat_addr_str[INET6_ADDRSTRLEN]; logmsg(ANDROID_LOG_INFO, "Detecting NAT64 prefix from DNS..."); - result = NULL; - plat_addr_set = 0; - ipv4_records = ipv6_records = 0; - - bzero(&hints, sizeof(hints)); - hints.ai_family = AF_UNSPEC; status = android_getaddrinfofornet(ipv4_name, NULL, &hints, net_id, MARK_UNSET, &result); - if(status != 0) { - logmsg(ANDROID_LOG_ERROR,"plat_prefix/dns(%s) status = %d/%s\n", ipv4_name, status, gai_strerror(status)); + if (status != 0 || result == NULL) { + logmsg(ANDROID_LOG_ERROR, "plat_prefix/dns(%s) status = %d/%s", + ipv4_name, status, gai_strerror(status)); return 0; } - for(p = result; p; p = p->ai_next) { - if(p->ai_family == AF_INET) { - ipv4_records++; - continue; - } - if(p->ai_family != AF_INET6) { - logmsg(ANDROID_LOG_WARN,"plat_prefix/unexpected address family: %d\n", p->ai_family); - continue; - } - ipv6_records++; - this_addr = (struct sockaddr_in6 *)p->ai_addr; - this_plat_addr = this_addr->sin6_addr; - this_plat_addr.s6_addr32[3] = 0; - - if(!plat_addr_set) { - plat_addr = this_plat_addr; - plat_addr_set = 1; - continue; - } + // Use only the first result. If other records are present, possibly with + // differing DNS64 prefixes they are ignored (there is very little sensible + // that could be done with them at this time anyway). - inet_ntop(AF_INET6, &plat_addr, plat_addr_str, sizeof(plat_addr_str)); - if(!IN6_ARE_ADDR_EQUAL(&plat_addr, &this_plat_addr)) { - char this_plat_addr_str[INET6_ADDRSTRLEN]; - inet_ntop(AF_INET6, &this_plat_addr, this_plat_addr_str, sizeof(this_plat_addr_str)); - logmsg(ANDROID_LOG_ERROR,"plat_prefix/two different plat addrs = %s,%s", - plat_addr_str,this_plat_addr_str); - } - } - if(result != NULL) { - freeaddrinfo(result); - } - if(ipv4_records > 0 && ipv6_records == 0) { - logmsg(ANDROID_LOG_WARN,"plat_prefix/no dns64 detected\n"); - return -1; + if (result->ai_family != AF_INET6) { + logmsg(ANDROID_LOG_WARN, "plat_prefix/unexpected address family: %d", result->ai_family); + return 0; } + plat_addr = ((struct sockaddr_in6 *)result->ai_addr)->sin6_addr; + // Only /96 DNS64 prefixes are supported at this time. + plat_addr.s6_addr32[3] = 0; + freeaddrinfo(result); - logmsg(ANDROID_LOG_INFO, "Detected NAT64 prefix %s/96", plat_addr_str); + logmsg(ANDROID_LOG_INFO, "Detected NAT64 prefix %s/96", + inet_ntop(AF_INET6, &plat_addr, plat_addr_str, sizeof(plat_addr_str))); *prefix = plat_addr; return 1; } |