On Fri, 12 Jun 2026 17:12:17 +0800 Xingui Yang <[email protected]> wrote:
> Add a new padding mode to the txonly forwarding engine, which allows > sending packets with configurable small sizes without standard L2/L3 > headers. This is useful for testing NIC padding logic. > > When padding mode is enabled via --tx-pkt-pad-mode flag: > - l2_len and l3_len are set to 0 instead of standard header lengths > - Packet data is filled with a static pattern instead of > Ethernet/IP/UDP headers > - Minimum packet length validation is bypassed to allow small > packet sizes (e.g., set txpkts 14) > > Signed-off-by: Xingui Yang <[email protected]> > Signed-off-by: Huisong Li <[email protected]> > --- > v2: Fix compilation exception of unterminated-string-initialization > --- What about something like this (*not tested*) patch. From 84ff35849f9881a93eed65ccd43a5cd1197cecb8 Mon Sep 17 00:00:00 2001 From: Stephen Hemminger <[email protected]> Date: Fri, 12 Jun 2026 09:10:17 -0700 Subject: [PATCH] testpnd: allow configuring runt frames Allow setting transmit size to be a small value which has ethernet header but no IP or UDP header. --- app/test-pmd/config.c | 12 +++---- app/test-pmd/txonly.c | 35 +++++++++++++++++++-- doc/guides/testpmd_app_ug/testpmd_funcs.rst | 13 ++++++++ 3 files changed, 51 insertions(+), 9 deletions(-) diff --git a/app/test-pmd/config.c b/app/test-pmd/config.c index 9d457ca88e..46ff678b9f 100644 --- a/app/test-pmd/config.c +++ b/app/test-pmd/config.c @@ -6327,9 +6327,6 @@ set_tx_pkt_segments(unsigned int *seg_lengths, unsigned int nb_segs) /* * Check that each segment length is greater or equal than * the mbuf data size. - * Check also that the total packet length is greater or equal than the - * size of an empty UDP/IP packet (sizeof(struct rte_ether_hdr) + - * 20 + 8). */ tx_pkt_len = 0; for (i = 0; i < nb_segs; i++) { @@ -6341,10 +6338,11 @@ set_tx_pkt_segments(unsigned int *seg_lengths, unsigned int nb_segs) } tx_pkt_len = (uint16_t)(tx_pkt_len + seg_lengths[i]); } - if (tx_pkt_len < (sizeof(struct rte_ether_hdr) + 20 + 8)) { - fprintf(stderr, "total packet length=%u < %d - give up\n", - (unsigned) tx_pkt_len, - (int)(sizeof(struct rte_ether_hdr) + 20 + 8)); + + /* Allow runt packets this is a test tool. */ + if (tx_pkt_len < (sizeof(struct rte_ether_hdr))) { + fprintf(stderr, "total packet length=%u < %zu - give up\n", + tx_pkt_len, sizeof(struct rte_ether_hdr)); return; } diff --git a/app/test-pmd/txonly.c b/app/test-pmd/txonly.c index 64893fa205..2e0abe361e 100644 --- a/app/test-pmd/txonly.c +++ b/app/test-pmd/txonly.c @@ -76,6 +76,12 @@ copy_buf_to_pkt_segs(void* buf, unsigned len, struct rte_mbuf *pkt, while (offset >= seg->data_len) { offset -= seg->data_len; seg = seg->next; + /* + * The packet may be shorter than the header stack when + * generating runt frames; stop once it runs out of segments. + */ + if (seg == NULL) + return; } copy_len = seg->data_len - offset; seg_buf = rte_pktmbuf_mtod_offset(seg, char *, offset); @@ -84,6 +90,8 @@ copy_buf_to_pkt_segs(void* buf, unsigned len, struct rte_mbuf *pkt, len -= copy_len; buf = ((char*) buf + copy_len); seg = seg->next; + if (seg == NULL) + return; seg_buf = rte_pktmbuf_mtod(seg, char *); copy_len = seg->data_len; } @@ -193,7 +201,6 @@ pkt_burst_prepare(struct rte_mbuf *pkt, struct rte_mempool *mbp, pkt->vlan_tci = vlan_tci; pkt->vlan_tci_outer = vlan_tci_outer; pkt->l2_len = sizeof(struct rte_ether_hdr); - pkt->l3_len = sizeof(struct rte_ipv4_hdr); pkt_len = pkt->data_len; pkt_seg = pkt; @@ -204,6 +211,24 @@ pkt_burst_prepare(struct rte_mbuf *pkt, struct rte_mempool *mbp, pkt_len += pkt_seg->data_len; } pkt_seg->next = NULL; /* Last segment of packet. */ + + /* + * A runt frame may be too short to carry a full IPv4/UDP header. + * Clamp l3_len and drop any checksum offload whose header is not + * fully present, so the PMD is never asked to checksum bytes that + * are not in the frame. pkt_len is at least sizeof(rte_ether_hdr), + * so the subtraction below cannot underflow. + */ + pkt->l3_len = RTE_MIN(sizeof(struct rte_ipv4_hdr), + pkt_len - sizeof(struct rte_ether_hdr)); + if (pkt_len < sizeof(struct rte_ether_hdr) + + sizeof(struct rte_ipv4_hdr)) + pkt->ol_flags &= ~(RTE_MBUF_F_TX_IP_CKSUM | + RTE_MBUF_F_TX_L4_MASK); + else if (pkt_len < sizeof(struct rte_ether_hdr) + + sizeof(struct rte_ipv4_hdr) + + sizeof(struct rte_udp_hdr)) + pkt->ol_flags &= ~RTE_MBUF_F_TX_L4_MASK; /* * Copy headers in first packet segment(s). */ @@ -405,7 +430,13 @@ tx_only_begin(portid_t pi) pkt_hdr_len = (uint16_t)(sizeof(struct rte_ether_hdr) + sizeof(struct rte_ipv4_hdr) + sizeof(struct rte_udp_hdr)); - pkt_data_len = tx_pkt_length - pkt_hdr_len; + /* + * tx_pkt_length may be smaller than the full header stack when + * generating runt frames; clamp the payload length to zero in that + * case so the IP/UDP length fields stay sane. + */ + pkt_data_len = tx_pkt_length > pkt_hdr_len ? + tx_pkt_length - pkt_hdr_len : 0; if ((tx_pkt_split == TX_PKT_SPLIT_RND || txonly_multi_flow) && tx_pkt_seg_lengths[0] < pkt_hdr_len) { diff --git a/doc/guides/testpmd_app_ug/testpmd_funcs.rst b/doc/guides/testpmd_app_ug/testpmd_funcs.rst index f0f2b0758b..d2e5b63586 100644 --- a/doc/guides/testpmd_app_ug/testpmd_funcs.rst +++ b/doc/guides/testpmd_app_ug/testpmd_funcs.rst @@ -876,6 +876,19 @@ Set the length of each segment of the TX-ONLY packets or length of packet for FL Where x[,y]* represents a CSV list of values, without white space. +The total packet length may be set as small as the Ethernet header +(``sizeof(struct rte_ether_hdr)``), which is below the size of an empty +UDP/IPv4 packet. This generates runt frames with a truncated (or absent) +IPv4/UDP header, which is useful for testing how a driver handles +undersized frames. Any header bytes that do not fit in the requested +length are simply not emitted. Checksum offloads are automatically +dropped for a frame too short to contain the corresponding header. + +Note that random split (``set txsplit rand``) and multi-flow +(``set txonly-flows``) still require the first segment to hold the full +Ethernet/IPv4/UDP header stack, so they cannot be combined with runt +lengths. + set txtimes ~~~~~~~~~~~ -- 2.53.0
