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test: handle zero-length udp datagram (#4344)

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Under rare but benign circumstances (on XNU), incoming datagrams appear
to be dropped by the operating system after libuv has been notified of
their arrival but before libuv has had a chance to receive them.

Fixes: https://github.com/libuv/libuv/issues/4219
This commit is contained in:
Ben Noordhuis 2024-07-29 22:30:08 +02:00 committed by GitHub
parent 47c833675b
commit 593aa3b2f6
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1 changed files with 14 additions and 7 deletions
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21
test/test-udp-recv-in-a-row.c
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@ -50,11 +50,16 @@ static void sv_recv_cb(uv_udp_t* handle,
const uv_buf_t* rcvbuf,
const struct sockaddr* addr,
unsigned flags) {
if (++ recv_cnt < N) {
ASSERT_EQ(sizeof(send_data), nread);
} else {
ASSERT_OK(nread);
}
/* |nread| can be zero when the kernel drops an incoming datagram after
* marking the file descriptor as readable but before libuv has a chance
* to receive it. Libuv still invokes the uv_udp_recv_cb callback to give
* back the memory from the uv_alloc_cb callback.
*
* See https://github.com/libuv/libuv/issues/4219.
*/
recv_cnt++;
if (nread > 0)
ASSERT_EQ(nread, sizeof(send_data));
}
static void check_cb(uv_check_t* handle) {
@ -63,9 +68,11 @@ static void check_cb(uv_check_t* handle) {
/**
* sv_recv_cb() is called with nread set to zero to indicate
* there is no more udp packet in the kernel, so the actual
* recv_cnt is one larger than N.
* recv_cnt is up to one larger than N. UDP being what it is,
* packets can get dropped so don't assume an exact count.
*/
ASSERT_EQ(N+1, recv_cnt);
ASSERT_GE(recv_cnt, 1);
ASSERT_LE(recv_cnt, N+1);
check_cb_called = 1;
/* we are done */