On Wed, Sep 18, 2024 at 08:05:26AM +0200, Markus Armbruster wrote:David Gibson <david(a)gibson.dropbear.id.au> writes:I usually would too, but given we work pretty heavily with both plain buffers and iovs, I thought it was worth emphasising that this works on the former.write(2) might not write all the data it is given. Add a write_all_buf() helper to keep calling it until all the given data is written, or we get an error. Currently we use write_remainder() to do this operation in pcap_frame(). That's a little awkward since it requires constructing an iovec, and future changes we want to make to write_remainder() will be easier in terms of this single buffer helper. Signed-off-by: David Gibson <david(a)gibson.dropbear.id.au> --- pcap.c | 3 +-- util.c | 25 +++++++++++++++++++++++++ util.h | 1 + 3 files changed, 27 insertions(+), 2 deletions(-) diff --git a/pcap.c b/pcap.c index 46cc4b0d..e6b5ced4 100644 --- a/pcap.c +++ b/pcap.c @@ -86,9 +86,8 @@ static void pcap_frame(const struct iovec *iov, size_t iovcnt, .caplen = l2len, .len = l2len }; - struct iovec hiov = { &h, sizeof(h) }; - if (write_remainder(pcap_fd, &hiov, 1, 0) < 0 || + if (write_all_buf(pcap_fd, &h, sizeof(h)) < 0 || write_remainder(pcap_fd, iov, iovcnt, offset) < 0) debug_perror("Cannot log packet, length %zu", l2len); } diff --git a/util.c b/util.c index eede4e58..7db7c2e7 100644 --- a/util.c +++ b/util.c @@ -582,6 +582,31 @@ int do_clone(int (*fn)(void *), char *stack_area, size_t stack_size, int flags, #endif } +/* write_all_buf() - write all of a buffer to an fd + * @fd: File descriptor + * @buf: Pointer to base of buffer + * @len: Length of buffer + * + * Return: 0 on success, -1 on error (with errno set) + * + * #syscalls write + */ +int write_all_buf(int fd, const void *buf, size_t len)I'd call it write_all(), but that's strictly a matter of taste.Oh, good idea. -- David Gibson (he or they) | I'll have my music baroque, and my code david AT gibson.dropbear.id.au | minimalist, thank you, not the other way | around. http://www.ozlabs.org/~dgibson+{ + const char *p = buf; + size_t left = len; + + while (left) { + ssize_t rc = write(fd, p, left); + + if (rc < 0) + return -1;Loop when errno == EINTR?