diff options
Diffstat (limited to 'Utilities/cmcurl/lib/asyn-ares.c')
| -rw-r--r-- | Utilities/cmcurl/lib/asyn-ares.c | 157 |
1 files changed, 140 insertions, 17 deletions
diff --git a/Utilities/cmcurl/lib/asyn-ares.c b/Utilities/cmcurl/lib/asyn-ares.c index 5cfb2602df..8561a47246 100644 --- a/Utilities/cmcurl/lib/asyn-ares.c +++ b/Utilities/cmcurl/lib/asyn-ares.c @@ -5,7 +5,7 @@ * | (__| |_| | _ <| |___ * \___|\___/|_| \_\_____| * - * Copyright (C) 1998 - 2018, Daniel Stenberg, <daniel@haxx.se>, et al. + * Copyright (C) 1998 - 2019, Daniel Stenberg, <daniel@haxx.se>, et al. * * This software is licensed as described in the file COPYING, which * you should have received as part of this distribution. The terms @@ -68,7 +68,7 @@ #include "progress.h" # if defined(CURL_STATICLIB) && !defined(CARES_STATICLIB) && \ - (defined(WIN32) || defined(_WIN32) || defined(__SYMBIAN32__)) + (defined(WIN32) || defined(__SYMBIAN32__)) # define CARES_STATICLIB # endif # include <ares.h> @@ -89,8 +89,20 @@ struct ResolverResults { int num_pending; /* number of ares_gethostbyname() requests */ Curl_addrinfo *temp_ai; /* intermediary result while fetching c-ares parts */ int last_status; + struct curltime happy_eyeballs_dns_time; /* when this timer started, or 0 */ }; +/* How long we are willing to wait for additional parallel responses after + obtaining a "definitive" one. + + This is intended to equal the c-ares default timeout. cURL always uses that + default value. Unfortunately, c-ares doesn't expose its default timeout in + its API, but it is officially documented as 5 seconds. + + See query_completed_cb() for an explanation of how this is used. + */ +#define HAPPY_EYEBALLS_DNS_TIMEOUT 5000 + /* * Curl_resolver_global_init() - the generic low-level asynchronous name * resolve API. Called from curl_global_init() to initialize global resolver @@ -119,6 +131,17 @@ void Curl_resolver_global_cleanup(void) #endif } + +static void Curl_ares_sock_state_cb(void *data, ares_socket_t socket_fd, + int readable, int writable) +{ + struct Curl_easy *easy = data; + if(!readable && !writable) { + DEBUGASSERT(easy); + Curl_multi_closed(easy, socket_fd); + } +} + /* * Curl_resolver_init() * @@ -126,9 +149,14 @@ void Curl_resolver_global_cleanup(void) * URL-state specific environment ('resolver' member of the UrlState * structure). Fills the passed pointer by the initialized ares_channel. */ -CURLcode Curl_resolver_init(void **resolver) +CURLcode Curl_resolver_init(struct Curl_easy *easy, void **resolver) { - int status = ares_init((ares_channel*)resolver); + int status; + struct ares_options options; + int optmask = ARES_OPT_SOCK_STATE_CB; + options.sock_state_cb = Curl_ares_sock_state_cb; + options.sock_state_cb_data = easy; + status = ares_init_options((ares_channel*)resolver, &options, optmask); if(status != ARES_SUCCESS) { if(status == ARES_ENOMEM) return CURLE_OUT_OF_MEMORY; @@ -159,12 +187,15 @@ void Curl_resolver_cleanup(void *resolver) * environment ('resolver' member of the UrlState structure). Duplicates the * 'from' ares channel and passes the resulting channel to the 'to' pointer. */ -int Curl_resolver_duphandle(void **to, void *from) +CURLcode Curl_resolver_duphandle(struct Curl_easy *easy, void **to, void *from) { - /* Clone the ares channel for the new handle */ - if(ARES_SUCCESS != ares_dup((ares_channel*)to, (ares_channel)from)) - return CURLE_FAILED_INIT; - return CURLE_OK; + (void)from; + /* + * it would be better to call ares_dup instead, but right now + * it is not possible to set 'sock_state_cb_data' outside of + * ares_init_options + */ + return Curl_resolver_init(easy, to); } static void destroy_async_data(struct Curl_async *async); @@ -180,6 +211,17 @@ void Curl_resolver_cancel(struct connectdata *conn) } /* + * We're equivalent to Curl_resolver_cancel() for the c-ares resolver. We + * never block. + */ +void Curl_resolver_kill(struct connectdata *conn) +{ + /* We don't need to check the resolver state because we can be called safely + at any time and we always do the same thing. */ + Curl_resolver_cancel(conn); +} + +/* * destroy_async_data() cleans up async resolver data. */ static void destroy_async_data(struct Curl_async *async) @@ -289,9 +331,9 @@ static int waitperform(struct connectdata *conn, int timeout_ms) /* move through the descriptors and ask for processing on them */ for(i = 0; i < num; i++) ares_process_fd((ares_channel)data->state.resolver, - pfd[i].revents & (POLLRDNORM|POLLIN)? + (pfd[i].revents & (POLLRDNORM|POLLIN))? pfd[i].fd:ARES_SOCKET_BAD, - pfd[i].revents & (POLLWRNORM|POLLOUT)? + (pfd[i].revents & (POLLWRNORM|POLLOUT))? pfd[i].fd:ARES_SOCKET_BAD); } return nfds; @@ -317,6 +359,29 @@ CURLcode Curl_resolver_is_resolved(struct connectdata *conn, waitperform(conn, 0); + /* Now that we've checked for any last minute results above, see if there are + any responses still pending when the EXPIRE_HAPPY_EYEBALLS_DNS timer + expires. */ + if(res + && res->num_pending + /* This is only set to non-zero if the timer was started. */ + && (res->happy_eyeballs_dns_time.tv_sec + || res->happy_eyeballs_dns_time.tv_usec) + && (Curl_timediff(Curl_now(), res->happy_eyeballs_dns_time) + >= HAPPY_EYEBALLS_DNS_TIMEOUT)) { + /* Remember that the EXPIRE_HAPPY_EYEBALLS_DNS timer is no longer + running. */ + memset( + &res->happy_eyeballs_dns_time, 0, sizeof(res->happy_eyeballs_dns_time)); + + /* Cancel the raw c-ares request, which will fire query_completed_cb() with + ARES_ECANCELLED synchronously for all pending responses. This will + leave us with res->num_pending == 0, which is perfect for the next + block. */ + ares_cancel((ares_channel)data->state.resolver); + DEBUGASSERT(res->num_pending == 0); + } + if(res && !res->num_pending) { if(dns) { (void)Curl_addrinfo_callback(conn, res->last_status, res->temp_ai); @@ -342,13 +407,13 @@ CURLcode Curl_resolver_is_resolved(struct connectdata *conn, /* * Curl_resolver_wait_resolv() * - * waits for a resolve to finish. This function should be avoided since using + * Waits for a resolve to finish. This function should be avoided since using * this risk getting the multi interface to "hang". * * If 'entry' is non-NULL, make it point to the resolved dns entry * - * Returns CURLE_COULDNT_RESOLVE_HOST if the host was not resolved, and - * CURLE_OPERATION_TIMEDOUT if a time-out occurred. + * Returns CURLE_COULDNT_RESOLVE_HOST if the host was not resolved, + * CURLE_OPERATION_TIMEDOUT if a time-out occurred, or other errors. */ CURLcode Curl_resolver_wait_resolv(struct connectdata *conn, struct Curl_dns_entry **entry) @@ -425,9 +490,7 @@ CURLcode Curl_resolver_wait_resolv(struct connectdata *conn, if(result) /* close the connection, since we can't return failure here without - cleaning up this connection properly. - TODO: remove this action from here, it is not a name resolver decision. - */ + cleaning up this connection properly. */ connclose(conn, "c-ares resolve failed"); return result; @@ -487,6 +550,66 @@ static void query_completed_cb(void *arg, /* (struct connectdata *) */ /* A successful result overwrites any previous error */ if(res->last_status != ARES_SUCCESS) res->last_status = status; + + /* If there are responses still pending, we presume they must be the + complementary IPv4 or IPv6 lookups that we started in parallel in + Curl_resolver_getaddrinfo() (for Happy Eyeballs). If we've got a + "definitive" response from one of a set of parallel queries, we need to + think about how long we're willing to wait for more responses. */ + if(res->num_pending + /* Only these c-ares status values count as "definitive" for these + purposes. For example, ARES_ENODATA is what we expect when there is + no IPv6 entry for a domain name, and that's not a reason to get more + aggressive in our timeouts for the other response. Other errors are + either a result of bad input (which should affect all parallel + requests), local or network conditions, non-definitive server + responses, or us cancelling the request. */ + && (status == ARES_SUCCESS || status == ARES_ENOTFOUND)) { + /* Right now, there can only be up to two parallel queries, so don't + bother handling any other cases. */ + DEBUGASSERT(res->num_pending == 1); + + /* It's possible that one of these parallel queries could succeed + quickly, but the other could always fail or timeout (when we're + talking to a pool of DNS servers that can only successfully resolve + IPv4 address, for example). + + It's also possible that the other request could always just take + longer because it needs more time or only the second DNS server can + fulfill it successfully. But, to align with the philosophy of Happy + Eyeballs, we don't want to wait _too_ long or users will think + requests are slow when IPv6 lookups don't actually work (but IPv4 ones + do). + + So, now that we have a usable answer (some IPv4 addresses, some IPv6 + addresses, or "no such domain"), we start a timeout for the remaining + pending responses. Even though it is typical that this resolved + request came back quickly, that needn't be the case. It might be that + this completing request didn't get a result from the first DNS server + or even the first round of the whole DNS server pool. So it could + already be quite some time after we issued the DNS queries in the + first place. Without modifying c-ares, we can't know exactly where in + its retry cycle we are. We could guess based on how much time has + gone by, but it doesn't really matter. Happy Eyeballs tells us that, + given usable information in hand, we simply don't want to wait "too + much longer" after we get a result. + + We simply wait an additional amount of time equal to the default + c-ares query timeout. That is enough time for a typical parallel + response to arrive without being "too long". Even on a network + where one of the two types of queries is failing or timing out + constantly, this will usually mean we wait a total of the default + c-ares timeout (5 seconds) plus the round trip time for the successful + request, which seems bearable. The downside is that c-ares might race + with us to issue one more retry just before we give up, but it seems + better to "waste" that request instead of trying to guess the perfect + timeout to prevent it. After all, we don't even know where in the + c-ares retry cycle each request is. + */ + res->happy_eyeballs_dns_time = Curl_now(); + Curl_expire( + conn->data, HAPPY_EYEBALLS_DNS_TIMEOUT, EXPIRE_HAPPY_EYEBALLS_DNS); + } } } |