When downloading certificates, check for related failures

  o Minor bugfixes (consensus downloads):

    - If a consensus expires while we are waiting for certificates to download,

      stop waiting for certificates.

    - If we stop waiting for certificates less than a minute after we started

      downloading them, do not consider the certificate download failure a

      separate failure.

      Fixes bug 20533; bugfix on commit e0204f21 in 0.2.0.9-alpha.

 * fetching certs before we check whether there is a better one? */

#define DELAY_WHILE_FETCHING_CERTS (20*60)

/** What is the minimum time we need to have waited fetching certs, before we

 * increment the consensus download schedule on failure? */

#define MIN_DELAY_FOR_FETCH_CERT_STATUS_FAILURE (1*60)

/* Check if a downloaded consensus flavor should still wait for certificates

 * to download now.

 * If so, return 1. If not, fail dls and return 0. */

 * to download now. If we decide not to wait, check if enough time has passed

 * to consider the certificate download failure a separate failure. If so,

 * fail dls.

 * If waiting for certificates to download, return 1. If not, return 0. */

static int

check_consensus_waiting_for_certs(int flavor, time_t now,

                                  download_status_t *dls)

  waiting = &consensus_waiting_for_certs[flavor];

  if (waiting->consensus) {

    /* XXXX make sure this doesn't delay sane downloads. */

    if (waiting->set_at + DELAY_WHILE_FETCHING_CERTS > now) {

    if (waiting->set_at + DELAY_WHILE_FETCHING_CERTS > now &&

        waiting->consensus->valid_until > now) {

      return 1;

    } else {

      if (!waiting->dl_failed) {

        if (waiting->set_at + MIN_DELAY_FOR_FETCH_CERT_STATUS_FAILURE > now) {

          download_status_failed(dls, 0);

        }

        waiting->dl_failed=1;

      }

    }