On Tue, Sep 09, 2025 at 11:51 AM +02, Jakub Sitnicki wrote:
On Fri, Sep 05, 2025 at 01:11 PM +02, Michal Luczaj wrote:
try_recv() was meant to support both @expect_success cases, but all the callers use @expect_success=false anyway. Drop the unused logic and fold in MSG_DONTWAIT. Adapt callers.
Subtle change here: recv() return value of 0 will also be considered (an unexpected) success.
Signed-off-by: Michal Luczaj mhal@rbox.co
.../selftests/bpf/prog_tests/sockmap_redir.c | 25 +++++++++------------- 1 file changed, 10 insertions(+), 15 deletions(-)
diff --git a/tools/testing/selftests/bpf/prog_tests/sockmap_redir.c b/tools/testing/selftests/bpf/prog_tests/sockmap_redir.c index 9c461d93113db20de65ac353f92dfdbe32ffbd3b..c1bf1076e8152b7d83c3e07e2dce746b5a39cf7e 100644 --- a/tools/testing/selftests/bpf/prog_tests/sockmap_redir.c +++ b/tools/testing/selftests/bpf/prog_tests/sockmap_redir.c @@ -144,17 +144,14 @@ static void get_redir_params(struct redir_spec *redir, *redirect_flags = 0; } -static void try_recv(const char *prefix, int fd, int flags, bool expect_success) +static void fail_recv(const char *prefix, int fd, int more_flags) { ssize_t n; char buf;
- errno = 0;
- n = recv(fd, &buf, 1, flags);
- if (n < 0 && expect_success)
FAIL_ERRNO("%s: unexpected failure: retval=%zd", prefix, n);- if (!n && !expect_success)
FAIL("%s: expected failure: retval=%zd", prefix, n);
- n = recv(fd, &buf, 1, MSG_DONTWAIT | more_flags);
- if (n >= 0)
FAIL("%s: unexpected success: retval=%zd", prefix, n);}
This bit, which you highlighted in the description, I don't get.
If we're expecting to receive exactly one byte, why treat a short read as a succcess? Why not make it a strict "n != 1" check?
[...]
Nevermind. It makes sense now. We do want to report a failure for 0-len msg recv as well. You're effectively checking if the rcv queue is empty.
I'd add MSG_PEEK, to signal that we're _just checking_ if the socket is readable, and turn the check into the below to succeed only when queue is empty:
(n != -1 || (errno != EAGAIN && errno != EWOULDBLOCK))
It's a minor thing. Leaving it up to you. Either way:
Reviewed-by: Jakub Sitnicki jakub@cloudflare.com