f7db9fd5e7
safe_recv(..., len), when used on a blocking fd, will attempt to call recv and collect data until either EOF, a hard error, or len bytes are collected. The previous commit used safe_recv() in a blocking mode to read a single byte into a buffer that was larger than a byte. This would cause ndhc to stall as safe_recv() would try to fill that buffer when no more data would ever be sent. This issue would only happen if ndhc is supposed to run a script. Introduce and use safe_recv_once() that will correct this problem and fill the semantic gap for blocking fds. I add a new call because in some cases the above behavior might be required for a blocking fd, too. Note that the above issue is not a problem for nonblocking fds; the EAGAIN or EWOULDBLOCK path will return a short read.
65 lines
1.7 KiB
C
65 lines
1.7 KiB
C
// Copyright 2010-2022 Nicholas J. Kain <njkain at gmail dot com>
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// SPDX-License-Identifier: MIT
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#ifndef NCM_IO_H_
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#define NCM_IO_H_
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#include <unistd.h>
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#include <errno.h>
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#include <limits.h>
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#include <sys/socket.h>
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#include <sys/types.h>
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ssize_t safe_read(int fd, char *buf, size_t len);
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// Same as above, but will only call read one time.
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// Meant to be used with a blocking fd where we need <= len bytes.
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static inline ssize_t safe_read_once(int fd, char *buf, size_t len)
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{
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if (len > SSIZE_MAX) len = SSIZE_MAX;
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ssize_t r;
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for (;;) {
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r = read(fd, buf, len);
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if (r >= 0 || errno != EINTR) break;
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}
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return r;
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}
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ssize_t safe_write(int fd, const char *buf, size_t len);
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ssize_t safe_sendto(int fd, const char *buf, size_t len, int flags,
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const struct sockaddr *dest_addr, socklen_t addrlen);
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ssize_t safe_recv(int fd, char *buf, size_t len, int flags);
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// Same as above, but will only call read one time.
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// Meant to be used with a blocking fd where we need <= len bytes.
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static inline ssize_t safe_recv_once(int fd, char *buf, size_t len, int flags)
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{
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if (len > SSIZE_MAX) len = SSIZE_MAX;
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ssize_t r;
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for (;;) {
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r = recv(fd, buf, len, flags);
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if (r >= 0 || errno != EINTR) break;
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}
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return r;
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}
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static inline ssize_t safe_recvmsg(int fd, struct msghdr *msg, int flags)
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{
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ssize_t r;
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for (;;) {
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r = recvmsg(fd, msg, flags);
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if (r >= 0 || errno != EINTR) break;
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}
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return r;
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}
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static inline int safe_ftruncate(int fd, off_t length)
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{
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int r;
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for (;;) {
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r = ftruncate(fd, length);
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if (!r || errno != EINTR) break;
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}
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return r;
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}
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#endif
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