[PATCH v5 4/4] net/af_packet: add software checksum offload support
scott.k.mitch1 at gmail.com
scott.k.mitch1 at gmail.com
Tue Feb 3 08:07:40 CET 2026
From: Scott Mitchell <scott.k.mitch1 at gmail.com>
Add software checksum offload support and configurable TX poll
behavior to improve flexibility and performance.
Add rte_net_ip_udptcp_cksum_mbuf in rte_net.h which is shared
between rte_eth_tap and rte_eth_af_packet that supports
IPv4/UDP/TCP checksums in software due to hardware offload
and context propagation not being supported.
Signed-off-by: Scott Mitchell <scott.k.mitch1 at gmail.com>
---
Depends-on: patch-160679 ("eal: add __rte_may_alias and __rte_aligned to unaligned typedefs")
doc/guides/nics/features/afpacket.ini | 2 +
doc/guides/rel_notes/release_26_03.rst | 2 +
drivers/net/af_packet/rte_eth_af_packet.c | 42 ++++++++++----
drivers/net/tap/rte_eth_tap.c | 70 ++---------------------
lib/net/rte_net.c | 68 ++++++++++++++++++++++
lib/net/rte_net.h | 22 +++++++
6 files changed, 130 insertions(+), 76 deletions(-)
diff --git a/doc/guides/nics/features/afpacket.ini b/doc/guides/nics/features/afpacket.ini
index 391f79b173..4bb81c84ff 100644
--- a/doc/guides/nics/features/afpacket.ini
+++ b/doc/guides/nics/features/afpacket.ini
@@ -7,5 +7,7 @@
Link status = Y
Promiscuous mode = Y
MTU update = Y
+L3 checksum offload = Y
+L4 checksum offload = Y
Basic stats = Y
Stats per queue = Y
diff --git a/doc/guides/rel_notes/release_26_03.rst b/doc/guides/rel_notes/release_26_03.rst
index 3b6be19645..2946acce99 100644
--- a/doc/guides/rel_notes/release_26_03.rst
+++ b/doc/guides/rel_notes/release_26_03.rst
@@ -60,6 +60,8 @@ New Features
* Fixed kernel memory barrier protocol for memory availability
* Fixed shared memory frame overhead offset calculation
* Added ``txpollnotrdy`` devarg to avoid ``poll()`` blocking calls
+ * Added checksum offload support for ``IPV4_CKSUM``, ``UDP_CKSUM``,
+ and ``TCP_CKSUM``
Removed Items
-------------
diff --git a/drivers/net/af_packet/rte_eth_af_packet.c b/drivers/net/af_packet/rte_eth_af_packet.c
index 9df1b1fd4c..662341ffc7 100644
--- a/drivers/net/af_packet/rte_eth_af_packet.c
+++ b/drivers/net/af_packet/rte_eth_af_packet.c
@@ -10,6 +10,8 @@
#include <rte_string_fns.h>
#include <rte_mbuf.h>
#include <rte_atomic.h>
+#include <rte_ip.h>
+#include <rte_net.h>
#include <rte_bitops.h>
#include <ethdev_driver.h>
#include <ethdev_vdev.h>
@@ -101,6 +103,7 @@ struct pmd_internals {
struct pkt_tx_queue *tx_queue;
uint8_t vlan_strip;
uint8_t timestamp_offloading;
+ bool tx_sw_cksum;
};
static const char *valid_arguments[] = {
@@ -220,7 +223,7 @@ eth_af_packet_rx(void *queue, struct rte_mbuf **bufs, uint16_t nb_pkts)
/* account for the receive frame */
bufs[i] = mbuf;
num_rx++;
- num_rx_bytes += mbuf->pkt_len;
+ num_rx_bytes += rte_pktmbuf_pkt_len(mbuf);
}
pkt_q->framenum = framenum;
pkt_q->rx_pkts += num_rx;
@@ -256,6 +259,7 @@ eth_af_packet_tx(void *queue, struct rte_mbuf **bufs, uint16_t nb_pkts)
{
struct tpacket2_hdr *ppd;
struct rte_mbuf *mbuf;
+ struct rte_mbuf *seg;
uint8_t *pbuf;
unsigned int framecount, framenum;
struct pollfd pfd;
@@ -277,7 +281,7 @@ eth_af_packet_tx(void *queue, struct rte_mbuf **bufs, uint16_t nb_pkts)
mbuf = bufs[i];
/* Drop oversized packets. Insert VLAN if necessary */
- if (unlikely(mbuf->pkt_len > pkt_q->frame_data_size ||
+ if (unlikely(rte_pktmbuf_pkt_len(mbuf) > pkt_q->frame_data_size ||
((mbuf->ol_flags & RTE_MBUF_F_TX_VLAN) != 0 &&
rte_vlan_insert(&mbuf) != 0))) {
continue;
@@ -308,23 +312,32 @@ eth_af_packet_tx(void *queue, struct rte_mbuf **bufs, uint16_t nb_pkts)
pbuf = (uint8_t *)ppd + ETH_AF_PACKET_FRAME_OVERHEAD;
- ppd->tp_len = mbuf->pkt_len;
- ppd->tp_snaplen = mbuf->pkt_len;
+ if (pkt_q->sw_cksum) {
+ seg = rte_net_ip_udptcp_cksum_mbuf(mbuf);
+ if (!seg)
+ continue;
- struct rte_mbuf *tmp_mbuf = mbuf;
+ mbuf = seg;
+ bufs[i] = seg;
+ }
+
+ ppd->tp_len = rte_pktmbuf_pkt_len(mbuf);
+ ppd->tp_snaplen = rte_pktmbuf_pkt_len(mbuf);
+
+ seg = mbuf;
do {
- uint16_t data_len = rte_pktmbuf_data_len(tmp_mbuf);
- memcpy(pbuf, rte_pktmbuf_mtod(tmp_mbuf, void*), data_len);
+ uint16_t data_len = rte_pktmbuf_data_len(seg);
+ memcpy(pbuf, rte_pktmbuf_mtod(seg, void*), data_len);
pbuf += data_len;
- tmp_mbuf = tmp_mbuf->next;
- } while (tmp_mbuf);
+ seg = seg->next;
+ } while (seg);
/* release incoming frame and advance ring buffer */
tpacket_write_status(&ppd->tp_status, TP_STATUS_SEND_REQUEST);
if (++framenum >= framecount)
framenum = 0;
num_tx++;
- num_tx_bytes += mbuf->pkt_len;
+ num_tx_bytes += rte_pktmbuf_pkt_len(mbuf);
}
rte_pktmbuf_free_bulk(&bufs[0], i);
@@ -396,10 +409,13 @@ eth_dev_configure(struct rte_eth_dev *dev __rte_unused)
{
struct rte_eth_conf *dev_conf = &dev->data->dev_conf;
const struct rte_eth_rxmode *rxmode = &dev_conf->rxmode;
+ const struct rte_eth_txmode *txmode = &dev_conf->txmode;
struct pmd_internals *internals = dev->data->dev_private;
internals->vlan_strip = !!(rxmode->offloads & RTE_ETH_RX_OFFLOAD_VLAN_STRIP);
internals->timestamp_offloading = !!(rxmode->offloads & RTE_ETH_RX_OFFLOAD_TIMESTAMP);
+ internals->tx_sw_cksum = !!(txmode->offloads & (RTE_ETH_TX_OFFLOAD_IPV4_CKSUM |
+ RTE_ETH_TX_OFFLOAD_UDP_CKSUM | RTE_ETH_TX_OFFLOAD_TCP_CKSUM));
return 0;
}
@@ -417,7 +433,10 @@ eth_dev_info(struct rte_eth_dev *dev, struct rte_eth_dev_info *dev_info)
dev_info->max_tx_queues = (uint16_t)internals->nb_queues;
dev_info->min_rx_bufsize = ETH_AF_PACKET_ETH_OVERHEAD;
dev_info->tx_offload_capa = RTE_ETH_TX_OFFLOAD_MULTI_SEGS |
- RTE_ETH_TX_OFFLOAD_VLAN_INSERT;
+ RTE_ETH_TX_OFFLOAD_VLAN_INSERT |
+ RTE_ETH_TX_OFFLOAD_IPV4_CKSUM |
+ RTE_ETH_TX_OFFLOAD_UDP_CKSUM |
+ RTE_ETH_TX_OFFLOAD_TCP_CKSUM;
dev_info->rx_offload_capa = RTE_ETH_RX_OFFLOAD_VLAN_STRIP |
RTE_ETH_RX_OFFLOAD_TIMESTAMP;
@@ -618,6 +637,7 @@ eth_tx_queue_setup(struct rte_eth_dev *dev,
{
struct pmd_internals *internals = dev->data->dev_private;
+ internals->tx_queue[tx_queue_id].sw_cksum = internals->tx_sw_cksum;
dev->data->tx_queues[tx_queue_id] = &internals->tx_queue[tx_queue_id];
return 0;
diff --git a/drivers/net/tap/rte_eth_tap.c b/drivers/net/tap/rte_eth_tap.c
index 730f1859bd..c7ed6dfb8b 100644
--- a/drivers/net/tap/rte_eth_tap.c
+++ b/drivers/net/tap/rte_eth_tap.c
@@ -525,7 +525,6 @@ tap_write_mbufs(struct tx_queue *txq, uint16_t num_mbufs,
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;
int proto;
int n;
int j;
@@ -556,74 +555,15 @@ tap_write_mbufs(struct tx_queue *txq, uint16_t num_mbufs,
iovecs[k].iov_len = sizeof(pi);
k++;
- l4_ol_flags = mbuf->ol_flags & RTE_MBUF_F_TX_L4_MASK;
- if (txq->csum && (mbuf->ol_flags & RTE_MBUF_F_TX_IP_CKSUM ||
- l4_ol_flags == RTE_MBUF_F_TX_UDP_CKSUM ||
- l4_ol_flags == RTE_MBUF_F_TX_TCP_CKSUM)) {
- unsigned int hdrlens = mbuf->l2_len + mbuf->l3_len;
- uint16_t *l4_cksum;
- void *l3_hdr;
-
- if (l4_ol_flags == RTE_MBUF_F_TX_UDP_CKSUM)
- hdrlens += sizeof(struct rte_udp_hdr);
- else if (l4_ol_flags == RTE_MBUF_F_TX_TCP_CKSUM)
- hdrlens += sizeof(struct rte_tcp_hdr);
- else if (l4_ol_flags != RTE_MBUF_F_TX_L4_NO_CKSUM)
+ if (txq->csum) {
+ seg = rte_net_ip_udptcp_cksum_mbuf(mbuf);
+ if (!seg)
return -1;
- /* Support only packets with at least layer 4
- * header included in the first segment
- */
- if (rte_pktmbuf_data_len(mbuf) < hdrlens)
- return -1;
-
- /* To change checksums (considering that a mbuf can be
- * indirect, for example), copy l2, l3 and l4 headers
- * in a new segment and chain it to existing data
- */
- seg = rte_pktmbuf_copy(mbuf, mbuf->pool, 0, hdrlens);
- if (seg == NULL)
- return -1;
- rte_pktmbuf_adj(mbuf, hdrlens);
- rte_pktmbuf_chain(seg, mbuf);
- pmbufs[i] = mbuf = seg;
-
- l3_hdr = rte_pktmbuf_mtod_offset(mbuf, void *, mbuf->l2_len);
- if (mbuf->ol_flags & RTE_MBUF_F_TX_IP_CKSUM) {
- struct rte_ipv4_hdr *iph = l3_hdr;
-
- iph->hdr_checksum = 0;
- iph->hdr_checksum = rte_ipv4_cksum(iph);
- }
-
- if (l4_ol_flags == RTE_MBUF_F_TX_L4_NO_CKSUM)
- goto skip_l4_cksum;
-
- if (l4_ol_flags == RTE_MBUF_F_TX_UDP_CKSUM) {
- struct rte_udp_hdr *udp_hdr;
-
- udp_hdr = rte_pktmbuf_mtod_offset(mbuf, struct rte_udp_hdr *,
- mbuf->l2_len + mbuf->l3_len);
- l4_cksum = &udp_hdr->dgram_cksum;
- } else {
- struct rte_tcp_hdr *tcp_hdr;
-
- tcp_hdr = rte_pktmbuf_mtod_offset(mbuf, struct rte_tcp_hdr *,
- mbuf->l2_len + mbuf->l3_len);
- l4_cksum = &tcp_hdr->cksum;
- }
-
- *l4_cksum = 0;
- if (mbuf->ol_flags & RTE_MBUF_F_TX_IPV4) {
- *l4_cksum = rte_ipv4_udptcp_cksum_mbuf(mbuf, l3_hdr,
- mbuf->l2_len + mbuf->l3_len);
- } else {
- *l4_cksum = rte_ipv6_udptcp_cksum_mbuf(mbuf, l3_hdr,
- mbuf->l2_len + mbuf->l3_len);
- }
+ mbuf = seg;
+ pmbufs[i] = seg;
}
-skip_l4_cksum:
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 *);
diff --git a/lib/net/rte_net.c b/lib/net/rte_net.c
index 458b4814a9..1a0397bcd7 100644
--- a/lib/net/rte_net.c
+++ b/lib/net/rte_net.c
@@ -615,3 +615,71 @@ uint32_t rte_net_get_ptype(const struct rte_mbuf *m,
return pkt_type;
}
+
+RTE_EXPORT_EXPERIMENTAL_SYMBOL(rte_net_ip_udptcp_cksum_mbuf, 26.03)
+struct rte_mbuf *
+rte_net_ip_udptcp_cksum_mbuf(struct rte_mbuf *mbuf)
+{
+ const uint64_t l4_ol_flags = mbuf->ol_flags & RTE_MBUF_F_TX_L4_MASK;
+ const uint32_t l4_offset = mbuf->l2_len + mbuf->l3_len;
+ uint32_t hdrlens = l4_offset;
+ unaligned_uint16_t *l4_cksum = NULL;
+ void *l3_hdr;
+
+ /* Quick check - nothing to do if no checksum offloads requested */
+ if (!(mbuf->ol_flags & (RTE_MBUF_F_TX_IP_CKSUM | RTE_MBUF_F_TX_L4_MASK)))
+ return mbuf;
+
+ /* Determine total header length needed */
+ if (l4_ol_flags == RTE_MBUF_F_TX_UDP_CKSUM)
+ hdrlens += sizeof(struct rte_udp_hdr);
+ else if (l4_ol_flags == RTE_MBUF_F_TX_TCP_CKSUM)
+ hdrlens += sizeof(struct rte_tcp_hdr);
+ else if (l4_ol_flags != RTE_MBUF_F_TX_L4_NO_CKSUM)
+ return NULL; /* Unsupported L4 checksum type */
+
+ /* Validate we at least have L2+L3 headers */
+ if (unlikely(rte_pktmbuf_data_len(mbuf) < l4_offset))
+ return NULL;
+
+ if (!RTE_MBUF_DIRECT(mbuf) || rte_mbuf_refcnt_read(mbuf) > 1) {
+ /* Indirect or shared - must copy, cannot modify in-place */
+ struct rte_mbuf *seg = rte_pktmbuf_copy(mbuf, mbuf->pool, 0, hdrlens);
+ if (!seg)
+ return NULL;
+
+ rte_pktmbuf_adj(mbuf, hdrlens);
+ rte_pktmbuf_chain(seg, mbuf);
+ mbuf = seg;
+ } else if (rte_pktmbuf_data_len(mbuf) < hdrlens &&
+ (rte_pktmbuf_linearize(mbuf) < 0 || rte_pktmbuf_data_len(mbuf) < hdrlens)) {
+ /* failed: direct, non-shared, but segmented headers linearize in-place */
+ return NULL;
+ }
+ /* else: Direct, non-shared, contiguous - can modify in-place, nothing to do */
+
+ l3_hdr = rte_pktmbuf_mtod_offset(mbuf, void *, mbuf->l2_len);
+
+ /* IPv4 header checksum */
+ if (mbuf->ol_flags & RTE_MBUF_F_TX_IP_CKSUM) {
+ struct rte_ipv4_hdr *iph = (struct rte_ipv4_hdr *)l3_hdr;
+ iph->hdr_checksum = 0;
+ iph->hdr_checksum = rte_ipv4_cksum(iph);
+ }
+
+ /* L4 checksum */
+ if (l4_ol_flags == RTE_MBUF_F_TX_UDP_CKSUM)
+ l4_cksum = &rte_pktmbuf_mtod_offset(mbuf, struct rte_udp_hdr *,
+ l4_offset)->dgram_cksum;
+ else if (l4_ol_flags == RTE_MBUF_F_TX_TCP_CKSUM)
+ l4_cksum = &rte_pktmbuf_mtod_offset(mbuf, struct rte_tcp_hdr *, l4_offset)->cksum;
+
+ if (l4_cksum) {
+ *l4_cksum = 0;
+ *l4_cksum = (mbuf->ol_flags & RTE_MBUF_F_TX_IPV4) ?
+ rte_ipv4_udptcp_cksum_mbuf(mbuf, l3_hdr, l4_offset) :
+ rte_ipv6_udptcp_cksum_mbuf(mbuf, l3_hdr, l4_offset);
+ }
+
+ return mbuf;
+}
diff --git a/lib/net/rte_net.h b/lib/net/rte_net.h
index 65d724b84b..b258a86928 100644
--- a/lib/net/rte_net.h
+++ b/lib/net/rte_net.h
@@ -246,6 +246,28 @@ rte_net_intel_cksum_prepare(struct rte_mbuf *m)
return rte_net_intel_cksum_flags_prepare(m, m->ol_flags);
}
+/**
+ * Compute IP and L4 checksums in software for mbufs with
+ * RTE_MBUF_F_TX_IP_CKSUM, RTE_MBUF_F_TX_UDP_CKSUM, or
+ * RTE_MBUF_F_TX_TCP_CKSUM offload flags set.
+ *
+ * On success, this function takes ownership of the input mbuf. The mbuf may be
+ * modified in-place (for direct, non-shared mbufs) or a new mbuf chain may be
+ * created (for indirect/shared mbufs) with the original becoming part of the chain.
+ *
+ * @param mbuf
+ * The packet mbuf to checksum.
+ * @return
+ * - On success: pointer to mbuf with checksums computed (may be same as input
+ * or a new mbuf chain). Caller must free only this returned pointer; the input
+ * mbuf pointer should not be freed separately as it may be part of the returned
+ * chain or may be the same as the returned pointer.
+ * - On error: NULL. Original mbuf remains valid and owned by caller.
+ */
+__rte_experimental
+struct rte_mbuf *
+rte_net_ip_udptcp_cksum_mbuf(struct rte_mbuf *mbuf);
+
#ifdef __cplusplus
}
#endif
--
2.39.5 (Apple Git-154)
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