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Diffstat (limited to 'src/basic/errno-util.h')
| -rw-r--r-- | src/basic/errno-util.h | 176 |
1 files changed, 176 insertions, 0 deletions
diff --git a/src/basic/errno-util.h b/src/basic/errno-util.h new file mode 100644 index 0000000..091f99c --- /dev/null +++ b/src/basic/errno-util.h @@ -0,0 +1,176 @@ +/* SPDX-License-Identifier: LGPL-2.1-or-later */ +#pragma once + +#include <stdlib.h> +#include <string.h> + +#include "macro.h" + +/* strerror(3) says that glibc uses a maximum length of 1024 bytes. */ +#define ERRNO_BUF_LEN 1024 + +/* Note: the lifetime of the compound literal is the immediately surrounding block, + * see C11 §6.5.2.5, and + * https://stackoverflow.com/questions/34880638/compound-literal-lifetime-and-if-blocks + * + * Note that we use the GNU variant of strerror_r() here. */ +#define STRERROR(errnum) strerror_r(abs(errnum), (char[ERRNO_BUF_LEN]){}, ERRNO_BUF_LEN) + +/* A helper to print an error message or message for functions that return 0 on EOF. + * Note that we can't use ({ … }) to define a temporary variable, so errnum is + * evaluated twice. */ +#define STRERROR_OR_EOF(errnum) ((errnum) != 0 ? STRERROR(errnum) : "Unexpected EOF") + +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) + +#define LOCAL_ERRNO(value) \ + PROTECT_ERRNO; \ + errno = abs(value) + +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 int RET_NERRNO(int ret) { + + /* Helper to wrap system calls in to make them return negative errno errors. This brings system call + * error handling in sync with how we usually handle errors in our own code, i.e. with immediate + * returning of negative errno. Usage is like this: + * + * … + * r = RET_NERRNO(unlink(t)); + * … + * + * or + * + * … + * fd = RET_NERRNO(open("/etc/fstab", O_RDONLY|O_CLOEXEC)); + * … + */ + + if (ret < 0) + return negative_errno(); + + return ret; +} + +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); +} + +/* For send()/recv() or read()/write(). */ +static inline bool ERRNO_IS_TRANSIENT(int r) { + return IN_SET(abs(r), + EAGAIN, + EINTR); +} + +/* 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) || + ERRNO_IS_TRANSIENT(r) || + abs(r) == 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 different errors for "not enough disk space" */ +static inline bool ERRNO_IS_DISK_SPACE(int r) { + return IN_SET(abs(r), + ENOSPC, + EDQUOT, + EFBIG); +} + +/* Three different errors for "this device does not quite exist" */ +static inline bool ERRNO_IS_DEVICE_ABSENT(int r) { + return IN_SET(abs(r), + ENODEV, + ENXIO, + ENOENT); +} + +/* Quite often we want to handle cases where the backing FS doesn't support extended attributes at all and + * where it simply doesn't have the requested xattr the same way */ +static inline bool ERRNO_IS_XATTR_ABSENT(int r) { + return abs(r) == ENODATA || + ERRNO_IS_NOT_SUPPORTED(r); +} |