1 files changed, 119 insertions, 0 deletions
diff --git a/src/basic/errno-util.h b/src/basic/errno-util.h
new file mode 100644
index 0000000..5609820
--- /dev/null
+++ b/src/basic/errno-util.h
@@ -0,0 +1,119 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+#pragma once
+
+#include <stdlib.h>
+#include <string.h>
+
+#include "macro.h"
+
+static inline void _reset_errno_(int *saved_errno) {
+        if (*saved_errno < 0) /* Invalidated by UNPROTECT_ERRNO? */
+                return;
+
+        errno = *saved_errno;
+}
+
+#define PROTECT_ERRNO                                                   \
+        _cleanup_(_reset_errno_) _unused_ int _saved_errno_ = errno
+
+#define UNPROTECT_ERRNO                         \
+        do {                                    \
+                errno = _saved_errno_;          \
+                _saved_errno_ = -1;             \
+        } while (false)
+
+static inline int negative_errno(void) {
+        /* This helper should be used to shut up gcc if you know 'errno' is
+         * negative. Instead of "return -errno;", use "return negative_errno();"
+         * It will suppress bogus gcc warnings in case it assumes 'errno' might
+         * be 0 and thus the caller's error-handling might not be triggered. */
+        assert_return(errno > 0, -EINVAL);
+        return -errno;
+}
+
+static inline const char *strerror_safe(int error) {
+        /* 'safe' here does NOT mean thread safety. */
+        return strerror(abs(error));
+}
+
+static inline int errno_or_else(int fallback) {
+        /* To be used when invoking library calls where errno handling is not defined clearly: we return
+         * errno if it is set, and the specified error otherwise. The idea is that the caller initializes
+         * errno to zero before doing an API call, and then uses this helper to retrieve a somewhat useful
+         * error code */
+        if (errno > 0)
+                return -errno;
+
+        return -abs(fallback);
+}
+
+/* Hint #1: ENETUNREACH happens if we try to connect to "non-existing" special IP addresses, such as ::5.
+ *
+ * Hint #2: The kernel sends e.g., EHOSTUNREACH or ENONET to userspace in some ICMP error cases.  See the
+ *          icmp_err_convert[] in net/ipv4/icmp.c in the kernel sources.
+ *
+ * Hint #3: When asynchronous connect() on TCP fails because the host never acknowledges a single packet,
+ *          kernel tells us that with ETIMEDOUT, see tcp(7). */
+static inline bool ERRNO_IS_DISCONNECT(int r) {
+        return IN_SET(abs(r),
+                      ECONNABORTED,
+                      ECONNREFUSED,
+                      ECONNRESET,
+                      EHOSTDOWN,
+                      EHOSTUNREACH,
+                      ENETDOWN,
+                      ENETRESET,
+                      ENETUNREACH,
+                      ENONET,
+                      ENOPROTOOPT,
+                      ENOTCONN,
+                      EPIPE,
+                      EPROTO,
+                      ESHUTDOWN,
+                      ETIMEDOUT);
+}
+
+/* Transient errors we might get on accept() that we should ignore. As per error handling comment in
+ * the accept(2) man page. */
+static inline bool ERRNO_IS_ACCEPT_AGAIN(int r) {
+        return ERRNO_IS_DISCONNECT(r) ||
+                IN_SET(abs(r),
+                       EAGAIN,
+                       EINTR,
+                       EOPNOTSUPP);
+}
+
+/* Resource exhaustion, could be our fault or general system trouble */
+static inline bool ERRNO_IS_RESOURCE(int r) {
+        return IN_SET(abs(r),
+                      EMFILE,
+                      ENFILE,
+                      ENOMEM);
+}
+
+/* Seven different errors for "operation/system call/ioctl/socket feature not supported" */
+static inline bool ERRNO_IS_NOT_SUPPORTED(int r) {
+        return IN_SET(abs(r),
+                      EOPNOTSUPP,
+                      ENOTTY,
+                      ENOSYS,
+                      EAFNOSUPPORT,
+                      EPFNOSUPPORT,
+                      EPROTONOSUPPORT,
+                      ESOCKTNOSUPPORT);
+}
+
+/* Two different errors for access problems */
+static inline bool ERRNO_IS_PRIVILEGE(int r) {
+        return IN_SET(abs(r),
+                      EACCES,
+                      EPERM);
+}
+
+/* Three difference errors for "not enough disk space" */
+static inline bool ERRNO_IS_DISK_SPACE(int r) {
+        return IN_SET(abs(r),
+                      ENOSPC,
+                      EDQUOT,
+                      EFBIG);
+}