From d378c68d74cb4fdac450650fe816c9d649c8edaf Mon Sep 17 00:00:00 2001 From: David 'Digit' Turner Date: Mon, 8 Mar 2010 15:13:04 -0800 Subject: [PATCH] Fix spurious DNS lookups in the C library. The problem was that the 'defdname' field of res_state structure was not properly initialized in __res_vinit(). This field is used to store the default domain name, which is normally build from calling gethostname() (see line 549 of res_init.c). Unfortunately, in the typical Android case, gethostname() returns an error (the hostname is configured) and a random stack string is used later to build the DNS search list (see lines 556+ in res_init.c) For the sake of illustration, let's say the search list is set to a random value like 'xWLK'. The end result is that when trying to result an unknown domain name (e.g. 'www.ptn'), the query fails then the resolver tries to make a new query with the DNS search list path(s) appended (e.g. 'www.ptn.xWLK'). The patch simply initializes 'defdname' to an empty string to avoid this when the net.dns.search system property is not set. Also contains whitespace/formatting fixes --- libc/docs/CHANGES.TXT | 4 ++++ libc/netbsd/resolv/res_cache.c | 2 +- libc/netbsd/resolv/res_init.c | 6 ++++-- libc/private/arpa_nameser.h | 8 ++++++++ libc/unistd/gethostname.c | 4 ++-- 5 files changed, 19 insertions(+), 5 deletions(-) diff --git a/libc/docs/CHANGES.TXT b/libc/docs/CHANGES.TXT index c0537144c..4f875473d 100644 --- a/libc/docs/CHANGES.TXT +++ b/libc/docs/CHANGES.TXT @@ -76,6 +76,10 @@ Differences between current and Android 2.1: - : Fix timezone management implementation to properly update 'tm_gmtoff' field in 'struct tm' structure. +- DNS: get rid of spurious random DNS queries when trying to resolve + an unknown domain name. Due to an initialization bug, a random DNS search + list was generated for each thread is net.dns.search is not defined. + ------------------------------------------------------------------------------- Differences between Android 2.1 and 2.0.1: diff --git a/libc/netbsd/resolv/res_cache.c b/libc/netbsd/resolv/res_cache.c index 2c912de41..2621a7bbf 100644 --- a/libc/netbsd/resolv/res_cache.c +++ b/libc/netbsd/resolv/res_cache.c @@ -251,7 +251,7 @@ _bprint( char* p, char* end, const char* format, ... ) return p; va_start(args, format); - n = snprintf( p, avail, format, args); + n = vsnprintf( p, avail, format, args); va_end(args); /* certain C libraries return -1 in case of truncation */ diff --git a/libc/netbsd/resolv/res_init.c b/libc/netbsd/resolv/res_init.c index 751603d43..81e570f77 100644 --- a/libc/netbsd/resolv/res_init.c +++ b/libc/netbsd/resolv/res_init.c @@ -198,6 +198,8 @@ int load_domain_search_list(res_state statp) { if (pp > statp->dnsrch) return 1; } + statp->defdname[0] = '\0'; /* no default domain name on Android */ + statp->dnsrch[0] = NULL; return 0; } #endif @@ -381,7 +383,7 @@ __res_vinit(res_state statp, int preinit) { /* Add the domain search list */ havesearch = load_domain_search_list(statp); -#else /* IGNORE resolv.conf */ +#else /* !ANDROID_CHANGES - IGNORE resolv.conf in Android */ #define MATCH(line, name) \ (!strncmp(line, name, sizeof(name) - 1) && \ (line[sizeof(name) - 1] == ' ' || \ @@ -534,7 +536,7 @@ __res_vinit(res_state statp, int preinit) { statp->nsort = nsort; (void) fclose(fp); } -#endif /* ANDROID_CHANGES */ +#endif /* !ANDROID_CHANGES */ /* * Last chance to get a nameserver. This should not normally * be necessary diff --git a/libc/private/arpa_nameser.h b/libc/private/arpa_nameser.h index 2d2a739d0..438dc0496 100644 --- a/libc/private/arpa_nameser.h +++ b/libc/private/arpa_nameser.h @@ -566,4 +566,12 @@ __END_DECLS #include "arpa_nameser_compat.h" #endif +#if 0 +# include +# define XLOG(...) \ + __libc_android_log_print(ANDROID_LOG_DEBUG,"libc",__VA_ARGS__) +#else +#define XLOG(...) do {} while (0) +#endif + #endif /* !_ARPA_NAMESER_H_ */ diff --git a/libc/unistd/gethostname.c b/libc/unistd/gethostname.c index 369d21ea5..5d3d7d962 100644 --- a/libc/unistd/gethostname.c +++ b/libc/unistd/gethostname.c @@ -41,11 +41,11 @@ int gethostname(char* buff, size_t buflen) int namelen = strlen(name.nodename); if ((int)buflen < namelen+1) { - errno = EINVAL; + errno = EINVAL; result = -1; } else { memcpy( buff, name.nodename, namelen+1 ); - } + } } return result; } -- 2.11.0