The previous code assumed a 1:1 mapping between virtqueue elements and iovec entries (enforced by an assert). Drop that assumption to allow elements that span multiple iovecs: track elem_used separately by walking the element list against the iov count returned after padding. This also fixes vu_queue_rewind() and vu_flush() to use the element count rather than the iov count. Use iov_tail_clone() in udp_vu_sock_recv() to handle header offset, replacing the manual base/len adjustment and restore pattern. Signed-off-by: Laurent Vivier Reviewed-by: David Gibson Reviewed-by: Jon Maloy --- udp_vu.c | 31 ++++++++++++++++--------------- 1 file changed, 16 insertions(+), 15 deletions(-) diff --git a/udp_vu.c b/udp_vu.c index dfff7bb1cd53..74bf79d57969 100644 --- a/udp_vu.c +++ b/udp_vu.c @@ -66,30 +66,25 @@ static size_t udp_vu_hdrlen(bool v6) */ static ssize_t udp_vu_sock_recv(struct iovec *iov, size_t *cnt, int s, bool v6) { + struct iovec msg_iov[VIRTQUEUE_MAX_SIZE]; struct msghdr msg = { 0 }; + struct iov_tail payload; size_t hdrlen, iov_used; ssize_t dlen; /* compute L2 header length */ hdrlen = udp_vu_hdrlen(v6); - /* reserve space for the headers */ - assert(iov[0].iov_len >= MAX(hdrlen, ETH_ZLEN + VNET_HLEN)); - iov[0].iov_base = (char *)iov[0].iov_base + hdrlen; - iov[0].iov_len -= hdrlen; + payload = IOV_TAIL(iov, *cnt, hdrlen); - /* read data from the socket */ - msg.msg_iov = iov; - msg.msg_iovlen = *cnt; + msg.msg_iov = msg_iov; + msg.msg_iovlen = iov_tail_clone(msg.msg_iov, payload.cnt, &payload); + /* read data from the socket */ dlen = recvmsg(s, &msg, 0); if (dlen < 0) return -1; - /* restore the pointer to the headers address */ - iov[0].iov_base = (char *)iov[0].iov_base - hdrlen; - iov[0].iov_len += hdrlen; - iov_used = iov_skip_bytes(iov, *cnt, MAX(dlen + hdrlen, VNET_HLEN + ETH_ZLEN), NULL); @@ -202,7 +197,7 @@ void udp_vu_sock_to_tap(const struct ctx *c, int s, int n, flow_sidx_t tosidx) } for (i = 0; i < n; i++) { - unsigned elem_cnt, elem_used; + unsigned elem_cnt, elem_used, j, k; size_t iov_cnt; ssize_t dlen; @@ -212,15 +207,21 @@ void udp_vu_sock_to_tap(const struct ctx *c, int s, int n, flow_sidx_t tosidx) if (elem_cnt == 0) break; - assert((size_t)elem_cnt == iov_cnt); /* one iovec per element */ - dlen = udp_vu_sock_recv(iov_vu, &iov_cnt, s, v6); if (dlen < 0) { vu_queue_rewind(vq, elem_cnt); break; } - elem_used = iov_cnt; /* one iovec per element */ + elem_used = 0; + for (j = 0, k = 0; k < iov_cnt && j < elem_cnt; j++) { + size_t iov_still_needed = iov_cnt - k; + + if (elem[j].in_num > iov_still_needed) + elem[j].in_num = iov_still_needed; + k += elem[j].in_num; + elem_used++; + } /* release unused buffers */ vu_queue_rewind(vq, elem_cnt - elem_used); -- 2.54.0