Commit 83f75c26 authored by Paolo Bonzini's avatar Paolo Bonzini
Browse files

iov: handle partial writes from sendmsg and recvmsg 



Partial writes can still happen in sendmsg and recvmsg, if a
signal is received in the middle of a write.  To handle this,
retry the operation with a new offset/bytes pair.

Reviewed-by: default avatarJuan Quintela <quintela@redhat.com>
Reviewed-by: default avatarOrit Wassermann <owasserm@redhat.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent f48869ad

util/iov.c

+55 −47
Original line number Diff line number Diff line
@@ -144,18 +144,12 @@ ssize_t iov_send_recv(int sockfd, struct iovec *iov, unsigned iov_cnt, 
                      size_t offset, size_t bytes,

                      bool do_send)

{

    ssize_t total = 0;

    ssize_t ret;

    size_t orig_len, tail;

    unsigned niov;



    if (bytes == 0) {

        /* Catch the do-nothing case early, as otherwise we will pass an

         * empty iovec to sendmsg/recvmsg(), and not all implementations

         * accept this.

         */

        return 0;

    }



    while (bytes > 0) {

        /* Find the start position, skipping `offset' bytes:

         * first, skip all full-sized vector elements, */

        for (niov = 0; niov < iov_cnt && offset >= iov[niov].iov_len; ++niov) {
@@ -163,7 +157,7 @@ ssize_t iov_send_recv(int sockfd, struct iovec *iov, unsigned iov_cnt, 
        }



        /* niov == iov_cnt would only be valid if bytes == 0, which

     * we already ruled out above.  */

         * we already ruled out in the loop condition.  */

        assert(niov < iov_cnt);

        iov += niov;

        iov_cnt -= niov;
@@ -191,7 +185,7 @@ ssize_t iov_send_recv(int sockfd, struct iovec *iov, unsigned iov_cnt, 


        ret = do_send_recv(sockfd, iov, niov, do_send);



    /* Undo the changes above */

        /* Undo the changes above before checking for errors */

        if (tail) {

            iov[niov-1].iov_len = orig_len;

        }
@@ -200,7 +194,21 @@ ssize_t iov_send_recv(int sockfd, struct iovec *iov, unsigned iov_cnt, 
            iov[0].iov_len += offset;

        }



    return ret;

        if (ret < 0) {

            assert(errno != EINTR);

            if (errno == EAGAIN && total > 0) {

                return total;

            }

            return -1;

        }



        /* Prepare for the next iteration */

        offset += ret;

        total += ret;

        bytes -= ret;

    }



    return total;

}