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.
91 lines
2.6 KiB
C
91 lines
2.6 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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#include "nk/io.h"
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// POSIX says read/write/etc() with len param > SSIZE_MAX is implementation defined.
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// So we avoid implementation-defined behavior with the bounding in each safe_* fn.
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/* returns -1 on error, >= 0 and equal to # chars read on success */
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ssize_t safe_read(int fd, char *buf, size_t len)
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{
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size_t s = 0;
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if (len > SSIZE_MAX) len = SSIZE_MAX;
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while (s < len) {
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ssize_t r = read(fd, buf + s, len - s);
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if (r == 0)
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break;
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if (r < 0) {
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if (errno == EINTR)
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continue;
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else if ((errno == EAGAIN || errno == EWOULDBLOCK) && s > 0)
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return (ssize_t)s;
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else
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return -1;
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}
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s += (size_t)r;
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}
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return (ssize_t)s;
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}
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/* returns -1 on error, >= 0 and equal to # chars written on success */
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ssize_t safe_write(int fd, const char *buf, size_t len)
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{
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size_t s = 0;
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if (len > SSIZE_MAX) len = SSIZE_MAX;
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while (s < len) {
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ssize_t r = write(fd, buf + s, len - s);
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if (r < 0) {
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if (errno == EINTR)
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continue;
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else if ((errno == EAGAIN || errno == EWOULDBLOCK) && s > 0)
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return (ssize_t)s;
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else
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return -1;
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}
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s += (size_t)r;
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}
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return (ssize_t)s;
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}
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/* returns -1 on error, >= 0 and equal to # chars written on success */
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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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{
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size_t s = 0;
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if (len > SSIZE_MAX) len = SSIZE_MAX;
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while (s < len) {
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ssize_t r = sendto(fd, buf + s, len - s, flags, dest_addr, addrlen);
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if (r < 0) {
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if (errno == EINTR)
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continue;
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else if ((errno == EAGAIN || errno == EWOULDBLOCK) && s > 0)
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return (ssize_t)s;
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else
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return -1;
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}
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s += (size_t)r;
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}
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return (ssize_t)s;
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}
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ssize_t safe_recv(int fd, char *buf, size_t len, int flags)
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{
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size_t s = 0;
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if (len > SSIZE_MAX) len = SSIZE_MAX;
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while (s < len) {
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ssize_t r = recv(fd, buf + s, len - s, flags);
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if (r == 0)
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break;
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if (r < 0) {
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if (errno == EINTR)
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continue;
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else if ((errno == EAGAIN || errno == EWOULDBLOCK) && s > 0)
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return (ssize_t)s;
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else
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return -1;
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}
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s += (size_t)r;
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}
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return (ssize_t)s;
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}
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