selftests: bpf: Use a temporary file in test_sockmap

Use a proper temporary file for sendpage tests. This means that running
the tests doesn't clutter the working directory, and allows running the
test on read-only filesystems.

Fixes: 16962b2 ("bpf: sockmap, add selftests")
Signed-off-by: Lorenz Bauer <[email protected]>
Signed-off-by: Daniel Borkmann <[email protected]>
Reviewed-by: Jakub Sitnicki <[email protected]>
Acked-by: Martin KaFai Lau <[email protected]>
Acked-by: John Fastabend <[email protected]>
Link: https://lore.kernel.org/bpf/[email protected]

Author: lmb

tools/testing/selftests/bpf/test_sockmap.c

@@ -331,7 +331,7 @@ static int msg_loop_sendpage(int fd, int iov_length, int cnt,
 	FILE *file;
 	int i, fp;
 
-	file = fopen(".sendpage_tst.tmp", "w+");
+	file = tmpfile();
 	if (!file) {
 		perror("create file for sendpage");
 		return 1;
@@ -340,33 +340,28 @@ static int msg_loop_sendpage(int fd, int iov_length, int cnt,
 		fwrite(&k, sizeof(char), 1, file);
 	fflush(file);
 	fseek(file, 0, SEEK_SET);
-	fclose(file);
 
-	fp = open(".sendpage_tst.tmp", O_RDONLY);
-	if (fp < 0) {
-		perror("reopen file for sendpage");
-		return 1;
-	}
+	fp = fileno(file);
 
 	clock_gettime(CLOCK_MONOTONIC, &s->start);
 	for (i = 0; i < cnt; i++) {
 		int sent = sendfile(fd, fp, NULL, iov_length);
 
 		if (!drop && sent < 0) {
 			perror("send loop error");
-			close(fp);
+			fclose(file);
 			return sent;
 		} else if (drop && sent >= 0) {
 			printf("sendpage loop error expected: %i\n", sent);
-			close(fp);
+			fclose(file);
 			return -EIO;
 		}
 
 		if (sent > 0)
 			s->bytes_sent += sent;
 	}
 	clock_gettime(CLOCK_MONOTONIC, &s->end);
-	close(fp);
+	fclose(file);
 	return 0;
 }