Replace the per-packet variable-length iovec array on the stack with a fixed-size array of TAP_MAX_TX_SEGS + 1 (129) entries, hoisted to function scope in tap_write_mbufs(). Packets with more than 128 segments are dropped.
This eliminates the last VLA in the driver. Signed-off-by: Stephen Hemminger <[email protected]> --- drivers/net/tap/rte_eth_tap.c | 14 ++++++++++++-- 1 file changed, 12 insertions(+), 2 deletions(-) diff --git a/drivers/net/tap/rte_eth_tap.c b/drivers/net/tap/rte_eth_tap.c index f2cf7da736..9efdbc7012 100644 --- a/drivers/net/tap/rte_eth_tap.c +++ b/drivers/net/tap/rte_eth_tap.c @@ -79,9 +79,15 @@ static_assert(RTE_PMD_TAP_MAX_QUEUES <= RTE_MP_MAX_FD_NUM, "TAP max queues excee */ #define TAP_MAX_RX_SEGS 128 +/* Limit on the number of segments per mbuf on Tx */ +#define TAP_MAX_TX_SEGS 128 + static_assert(TAP_MAX_RX_SEGS + 1 <= IOV_MAX, "TAP_MAX_RX_SEGS + 1 (for tun_pi) must not exceed IOV_MAX"); +static_assert(TAP_MAX_TX_SEGS + 1 <= IOV_MAX, + "TAP_MAX_TX_SEGS + 1 (for tun_pi) must not exceed IOV_MAX"); + #define TAP_RX_OFFLOAD (RTE_ETH_RX_OFFLOAD_SCATTER | \ RTE_ETH_RX_OFFLOAD_IPV4_CKSUM | \ RTE_ETH_RX_OFFLOAD_UDP_CKSUM | \ @@ -533,13 +539,13 @@ tap_write_mbufs(struct tx_queue *txq, uint16_t num_mbufs, uint16_t *num_packets, unsigned long *num_tx_bytes) { struct pmd_process_private *process_private; + struct iovec iovecs[TAP_MAX_TX_SEGS + 1]; int i; process_private = rte_eth_devices[txq->out_port].process_private; for (i = 0; i < num_mbufs; i++) { struct rte_mbuf *mbuf = pmbufs[i]; - struct iovec iovecs[mbuf->nb_segs + 2]; struct tun_pi pi = { .flags = 0, .proto = 0x00 }; struct rte_mbuf *seg = mbuf; uint64_t l4_ol_flags; @@ -641,6 +647,10 @@ tap_write_mbufs(struct tx_queue *txq, uint16_t num_mbufs, } skip_l4_cksum: + /* tun_pi header + packet segments must fit in iovecs */ + if (unlikely(mbuf->nb_segs > TAP_MAX_TX_SEGS)) + return -1; + for (j = 0; j < mbuf->nb_segs; j++) { iovecs[k].iov_len = rte_pktmbuf_data_len(seg); iovecs[k].iov_base = rte_pktmbuf_mtod(seg, void *); @@ -669,7 +679,7 @@ pmd_tx_burst(void *queue, struct rte_mbuf **bufs, uint16_t nb_pkts) uint16_t num_packets = 0; unsigned long num_tx_bytes = 0; uint32_t max_size; - int i; + unsigned int i; if (unlikely(nb_pkts == 0)) return 0; -- 2.51.0
