resolve: cache lookup for async resolvers

While waiting for a host resolve, check if the host cache may have
gotten the name already (by someone else), for when the same name is
resolved by several simultanoues requests.

The resolver thread occasionally gets stuck in getaddrinfo() when the
DNS or anything else is crappy or slow, so when a host is found in the
DNS cache, leave the thread alone and let itself cleanup the mess.

1 files changed, 11 insertions, 0 deletions

diff --git a/lib/hostip.h b/lib/hostip.h
index 42ed7d320..440465194 100644
--- a/lib/hostip.h
+++ b/lib/hostip.h
@@ -172,6 +172,17 @@ const char *Curl_printable_address(const Curl_addrinfo *ip,
                                    char *buf, size_t bufsize);
 
 /*
+ * Curl_fetch_addr() fetches a 'Curl_dns_entry' already in the DNS cache.
+ *
+ * Returns the Curl_dns_entry entry pointer or NULL if not in the cache.
+ */
+struct Curl_dns_entry *
+Curl_fetch_addr(struct connectdata *conn,
+                const char *hostname,
+                int port,
+                int *stale);
+
+/*
  * Curl_cache_addr() stores a 'Curl_addrinfo' struct in the DNS cache.
  *
  * Returns the Curl_dns_entry entry pointer or NULL if the storage failed.