bio_retry_tests.c

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/*
 *   This library is free software; you can redistribute it and/or
 *   modify it under the terms of the GNU Lesser General Public
 *   License as published by the Free Software Foundation; either
 *   version 2.1 of the License, or (at your option) any later version.
 *
 *   This library is distributed in the hope that it will be useful,
 *   but WITHOUT ANY WARRANTY; without even the implied warranty of
 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
 *   Lesser General Public License for more details.
 *
 *   You should have received a copy of the GNU Lesser General Public
 *   License along with this library; if not, write to the Free Software
 *   Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA
 */
 
/** Tests for the retry bio running out of entries
 *
 * @file src/lib/bio/test/bio_retry_tests.c
 *
 * @copyright 2026 Network RADIUS SAS (legal@networkradius.com)
 */
#include <freeradius-devel/util/test/acutest_common_init.h>
#include <freeradius-devel/util/test/acutest_helpers.h>
 
#define _BIO_PRIVATE 1
#include <freeradius-devel/bio/bio_priv.h>
#include <freeradius-devel/bio/null.h>
#include <freeradius-devel/bio/retry.h>
 
static int                      blocked_count;
static int                      resume_count;
static int                      release_count;
static fr_bio_retry_entry_t     *saved_item;
 
static fr_bio_t                 *resume_write_bio;      //!< when set, cb_write_resume() writes packet2 to this bio
static ssize_t                  resume_write_rcode;
 
static uint8_t                  packet1[4] = { 1, 2, 3, 4 };
static uint8_t                  packet2[4] = { 5, 6, 7, 8 };
 
static int      cb_noop(fr_bio_t *bio)          { (void) bio; return 0; }
static void     cb_noop_void(fr_bio_t *bio)     { (void) bio; }
static int      cb_write_blocked(fr_bio_t *bio) { (void) bio; blocked_count++; return 1; }
 
static int cb_write_resume(fr_bio_t *bio)
{
        (void) bio;
        resume_count++;
 
        if (resume_write_bio) resume_write_rcode = fr_bio_write(resume_write_bio, NULL, packet2, sizeof(packet2));
 
        return 1;
}
 
static fr_bio_cb_funcs_t test_cb = {
        .read_resume    = cb_noop,
        .write_resume   = cb_write_resume,
        .read_blocked   = cb_noop,
        .write_blocked  = cb_write_blocked,
        .eof            = cb_noop_void,
};
 
static void retry_sent(UNUSED fr_bio_t *bio, UNUSED void *packet_ctx, UNUSED const void *buffer, UNUSED size_t size,
                       fr_bio_retry_entry_t *retry_ctx)
{
        saved_item = retry_ctx;
}
 
static bool retry_response(UNUSED fr_bio_t *bio, UNUSED fr_bio_retry_entry_t **item_p, UNUSED void *packet_ctx,
                           UNUSED const void *buffer, UNUSED size_t size)
{
        return false;
}
 
static void retry_release(UNUSED fr_bio_t *bio, UNUSED fr_bio_retry_entry_t *retry_ctx,
                          UNUSED fr_bio_retry_release_reason_t reason)
{
        release_count++;
}
 
static size_t                   stub_bytes;             //!< bytes of packet data which the stub has accepted
 
/** A transport which accepts every write in full, and never has anything to read.
 */
static ssize_t stub_write_all(UNUSED fr_bio_t *bio, UNUSED void *packet_ctx, void const *buffer, size_t size)
{
        if (!buffer) return 0;          /* nothing to flush */
 
        stub_bytes += size;
        return size;
}
 
/** A transport which accepts one byte of each write, so the retry bio saves the rest of the packet.
 */
static ssize_t stub_write_one(UNUSED fr_bio_t *bio, UNUSED void *packet_ctx, void const *buffer, UNUSED size_t size)
{
        if (!buffer) return 0;
 
        stub_bytes++;
        return 1;
}
 
static fr_bio_t *stub_alloc(TALLOC_CTX *ctx)
{
        fr_bio_common_t *my;
 
        my = talloc_zero(ctx, fr_bio_common_t);
        if (!my) return NULL;
 
        my->bio.read = fr_bio_null_read;
        my->bio.write = stub_write_all;
 
        return &my->bio;
}
 
/** Allocate a retry bio with one entry, in front of a stub.
 *
 *  Only test_partial_retransmit() runs the timer list, so no timer fires in the other tests.
 */
static fr_bio_t *test_retry_alloc_full(TALLOC_CTX *ctx, fr_bio_retry_config_t *cfg, fr_time_delta_t mrd, size_t max_saved)
{
        fr_bio_t        *retry, *stub;
 
        blocked_count = resume_count = release_count = 0;
        stub_bytes = 0;
        saved_item = NULL;
        resume_write_bio = NULL;
        resume_write_rcode = 0;
 
        cfg->el = fr_event_list_alloc(ctx, NULL, NULL);
        if (!cfg->el) return NULL;
 
        cfg->retry_config = (fr_retry_config_t) {
                .irt = fr_time_delta_from_sec(2),
                .mrt = fr_time_delta_from_sec(16),
                .mrd = mrd,
                .mrc = 5,
        };
 
        stub = stub_alloc(ctx);
        if (!stub) return NULL;
 
        retry = fr_bio_retry_alloc(ctx, max_saved, retry_sent, retry_response, NULL, retry_release, cfg, stub);
        if (!retry) return NULL;
 
        fr_bio_cb_set(retry, &test_cb);
 
        return retry;
}
 
static fr_bio_t *test_retry_alloc_mrd(TALLOC_CTX *ctx, fr_bio_retry_config_t *cfg, fr_time_delta_t mrd)
{
        return test_retry_alloc_full(ctx, cfg, mrd, 1);
}
 
static fr_bio_t *test_retry_alloc(TALLOC_CTX *ctx, fr_bio_retry_config_t *cfg)
{
        return test_retry_alloc_mrd(ctx, cfg, fr_time_delta_from_sec(30));
}
 
/** Running out of entries blocks writes, and freeing an entry resumes writes.
 *
 *  See finding 1 in retry.md.  Only fr_bio_retry_write_resume() clears write_blocked, and
 *  fr_bio_retry_write_resume() runs only when the socket becomes writable.  If running out of
 *  entries set write_blocked, then the application would never resume writes.
 */
static void test_all_used_resumes(void)
{
        TALLOC_CTX              *ctx = talloc_init_const("test");
        fr_bio_retry_config_t   cfg;
        fr_bio_t                *retry;
 
        retry = test_retry_alloc(ctx, &cfg);
        TEST_CHECK(retry != NULL);
        if (!retry) goto done;
 
        TEST_CASE("the first packet uses the only entry");
        TEST_CHECK_RET((int) fr_bio_write(retry, NULL, packet1, sizeof(packet1)), (int) sizeof(packet1));
        TEST_CHECK(saved_item != NULL);
        if (!saved_item) goto done;
 
        TEST_CASE("the second write returns IO_WOULD_BLOCK, and the retry bio calls the write_blocked callback");
        TEST_CHECK(fr_bio_write(retry, NULL, packet2, sizeof(packet2)) == fr_bio_error(IO_WOULD_BLOCK));
        TEST_CHECK_RET(blocked_count, 1);
 
        TEST_CASE("running out of entries does not set write_blocked");
        TEST_CHECK(!fr_bio_retry_info(retry)->write_blocked);
 
        TEST_CASE("cancelling the entry calls the release callback and the resume callback");
        TEST_CHECK_RET(fr_bio_retry_entry_cancel(retry, saved_item), 1);
        TEST_CHECK_RET(release_count, 1);
        TEST_CHECK_RET(resume_count, 1);
 
        TEST_CASE("the retry bio now accepts the second packet");
        TEST_CHECK_RET((int) fr_bio_write(retry, NULL, packet2, sizeof(packet2)), (int) sizeof(packet2));
 
done:
        talloc_free(ctx);
}
 
/** The application may write from inside the resume callback, so fr_bio_retry_release() must put
 *  the freed entry on the free list before calling the resume callback.
 */
static void test_resume_can_write(void)
{
        TALLOC_CTX              *ctx = talloc_init_const("test");
        fr_bio_retry_config_t   cfg;
        fr_bio_t                *retry;
 
        retry = test_retry_alloc(ctx, &cfg);
        TEST_CHECK(retry != NULL);
        if (!retry) goto done;
 
        TEST_CHECK_RET((int) fr_bio_write(retry, NULL, packet1, sizeof(packet1)), (int) sizeof(packet1));
        TEST_CHECK(fr_bio_write(retry, NULL, packet2, sizeof(packet2)) == fr_bio_error(IO_WOULD_BLOCK));
        if (!saved_item) goto done;
 
        TEST_CASE("a write from inside the resume callback succeeds");
        resume_write_bio = retry;
        TEST_CHECK_RET(fr_bio_retry_entry_cancel(retry, saved_item), 1);
        TEST_CHECK_RET(resume_count, 1);
        TEST_CHECK_RET((int) resume_write_rcode, (int) sizeof(packet2));
 
        TEST_CASE("the retry bio did not call the write_blocked callback a second time");
        TEST_CHECK_RET(blocked_count, 1);
 
done:
        talloc_free(ctx);
}
 
/** The retry bio saves the rest of a partly written retransmission once, and a flush sends the rest once.
 *
 *  See finding 2 in retry.md.  Before the fix, fr_bio_retry_rewrite() saved the rest of the packet,
 *  and then fr_bio_retry_write_item() saved the rest of the packet again.
 */
static void test_partial_retransmit(void)
{
        TALLOC_CTX              *ctx = talloc_init_const("test");
        fr_bio_retry_config_t   cfg;
        fr_bio_t                *retry, *stub;
        fr_time_t               when;
 
        retry = test_retry_alloc(ctx, &cfg);
        TEST_CHECK(retry != NULL);
        if (!retry) goto done;
 
        stub = fr_bio_next(retry);
 
        TEST_CASE("the stub accepts the first transmission in full");
        TEST_CHECK_RET((int) fr_bio_write(retry, NULL, packet1, sizeof(packet1)), (int) sizeof(packet1));
        TEST_CHECK_RET((int) stub_bytes, (int) sizeof(packet1));
 
        TEST_CASE("the retransmission timer fires, and the stub accepts one byte");
        TEST_MSG("the initial retransmission time (irt) is 2s, so running the timer list 3s ahead fires exactly one retransmission");
        stub->write = stub_write_one;
        when = fr_time_add(fr_time(), fr_time_delta_from_sec(3));
        (void) fr_timer_list_run(cfg.el->tl, &when);
        TEST_CHECK_RET((int) stub_bytes, (int) sizeof(packet1) + 1);
 
        TEST_CASE("the retry bio has saved the rest of the packet and has blocked writes");
        TEST_CHECK(fr_bio_retry_info(retry)->write_blocked);
 
        TEST_CASE("a flush sends the rest of the packet exactly once");
        stub->write = stub_write_all;
        (void) fr_bio_write(retry, NULL, NULL, SIZE_MAX);
        TEST_CHECK_RET((int) stub_bytes, (int) (2 * sizeof(packet1)));
        TEST_CHECK(!fr_bio_retry_info(retry)->write_blocked);
 
done:
        talloc_free(ctx);
}
 
/** When the retry bio cannot save the rest of a partly written packet, the retry bio releases the entry of the packet.
 *
 *  See 'A related defect: a failed save kept the entry' in retry.md.  Without the release, the entry
 *  stays on both timer lists after the sent() callback has passed the entry to the application.  The
 *  write returns OOM, so an application which then frees the packet leaves the retry bio holding a
 *  pointer to freed memory.
 */
static void test_partial_oom_releases(void)
{
        TALLOC_CTX              *ctx = talloc_init_const("test");
        fr_bio_retry_config_t   cfg;
        fr_bio_t                *retry, *stub;
 
        retry = test_retry_alloc(ctx, &cfg);
        TEST_CHECK(retry != NULL);
        if (!retry) goto done;
 
        stub = fr_bio_next(retry);
 
        TEST_CASE("a partial write returns OOM when the retry bio cannot allocate the buffer for the rest of the packet");
        TEST_MSG("a talloc memory limit on the retry bio makes the buffer allocation fail");
DIAG_OFF(deprecated-declarations)
        TEST_CHECK(talloc_set_memlimit(retry, talloc_total_size(retry)) == 0);
DIAG_ON(deprecated-declarations)
        stub->write = stub_write_one;
        TEST_CHECK(fr_bio_write(retry, NULL, packet1, sizeof(packet1)) == fr_bio_error(OOM));
 
        TEST_CASE("the retry bio releases the entry");
        TEST_CHECK_RET(release_count, 1);
 
        TEST_CASE("the only entry is free again, so the retry bio accepts the next packet");
DIAG_OFF(deprecated-declarations)
        TEST_CHECK(talloc_set_memlimit(retry, 0) == 0);
DIAG_ON(deprecated-declarations)
        stub->write = stub_write_all;
        TEST_CHECK_RET((int) fr_bio_write(retry, NULL, packet2, sizeof(packet2)), (int) sizeof(packet2));
        TEST_CHECK_RET(blocked_count, 0);
 
done:
        talloc_free(ctx);
}
 
/** Blocking writes expires an overdue entry, and the expiry sees writes as blocked.
 *
 *  See finding 1 in retry.md.  Arming the expiry list runs any expiry which is already due, and
 *  fr_bio_retry_expiry_timer() asserts that writes are blocked.  fr_bio_retry_write_blocked() used to
 *  set the flag only after arming the list.
 */
static void test_block_expires_overdue(void)
{
        TALLOC_CTX              *ctx = talloc_init_const("test");
        fr_bio_retry_config_t   cfg;
        fr_bio_t                *retry;
        fr_bio_common_t         *common;
        fr_time_t               until;
 
        /*
         *      A maximum duration of one microsecond makes the entry overdue as soon as the entry is
         *      written.  fr_bio_retry_alloc() copies the retry configuration, so the duration has to be set
         *      before the bio is allocated.
         */
        retry = test_retry_alloc_mrd(ctx, &cfg, fr_time_delta_from_usec(1));
        TEST_CHECK(retry != NULL);
        if (!retry) goto done;
 
        TEST_CASE("the packet is written");
        TEST_CHECK_RET((int) fr_bio_write(retry, NULL, packet1, sizeof(packet1)), (int) sizeof(packet1));
 
        /*
         *      Make sure that the maximum duration has passed.  The wait is a few microseconds, so a busy
         *      loop is enough, and the result does not depend on how fast the test runs.
         */
        until = fr_time_add(fr_time(), fr_time_delta_from_usec(10));
        while (fr_time_lt(fr_time(), until)) { /* nothing */ }
 
        TEST_CASE("blocking writes runs the overdue expiry, which releases the entry");
        common = (fr_bio_common_t *) retry;
        TEST_CHECK(common->priv_cb.write_blocked != NULL);
        if (!common->priv_cb.write_blocked) goto done;
 
        TEST_CHECK_RET(common->priv_cb.write_blocked(retry), 1);
        TEST_CHECK_RET(release_count, 1);
        TEST_CHECK(fr_bio_retry_info(retry)->write_blocked);
 
        TEST_CASE("a released entry while blocked does not resume writes");
        TEST_CHECK_RET(resume_count, 0);
 
done:
        talloc_free(ctx);
}
 
/** When one retransmission blocks writes, the other retransmissions due in the same pass wait.
 *
 *  See finding 1 in retry.md.  fr_bio_retry_write_blocked() disarms the retry list, and the timer
 *  list used to keep running the other entries which were due in the same pass.
 */
static void test_block_stops_retries(void)
{
        TALLOC_CTX              *ctx = talloc_init_const("test");
        fr_bio_retry_config_t   cfg;
        fr_bio_t                *retry, *stub;
        fr_time_t               when;
 
        retry = test_retry_alloc_full(ctx, &cfg, fr_time_delta_from_sec(30), 2);
        TEST_CHECK(retry != NULL);
        if (!retry) goto done;
 
        stub = fr_bio_next(retry);
 
        TEST_CASE("two packets are written in full");
        TEST_CHECK_RET((int) fr_bio_write(retry, NULL, packet1, sizeof(packet1)), (int) sizeof(packet1));
        TEST_CHECK_RET((int) fr_bio_write(retry, NULL, packet2, sizeof(packet2)), (int) sizeof(packet2));
 
        TEST_CASE("both retransmissions are due, and the first one blocks writes");
        TEST_MSG("irt is 2s, so running the timer list 3s ahead makes both retransmissions due");
        stub->write = stub_write_one;
        when = fr_time_add(fr_time(), fr_time_delta_from_sec(3));
        (void) fr_timer_list_run(cfg.el->tl, &when);
 
        TEST_CASE("only the first retransmission was written, and writes are blocked");
        TEST_CHECK_RET((int) stub_bytes, (int) (sizeof(packet1) + sizeof(packet2) + 1));
        TEST_CHECK(fr_bio_retry_info(retry)->write_blocked);
 
done:
        talloc_free(ctx);
}
 
TEST_LIST = {
        { "all_used_resumes",           test_all_used_resumes },
        { "resume_can_write",           test_resume_can_write },
        { "partial_retransmit",         test_partial_retransmit },
        { "partial_oom_releases",       test_partial_oom_releases },
        { "block_expires_overdue",      test_block_expires_overdue },
        { "block_stops_retries",        test_block_stops_retries },
        TEST_TERMINATOR
};