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Miller" , Eric Dumazet , Paolo Abeni Cc: horms@kernel.org, michael.chan@broadcom.com, pavan.chebbi@broadcom.com, linux-kernel@vger.kernel.org, leon@kernel.org, Joe Damato Subject: [net-next v5 11/12] net: netdevsim: Add support for SW USO Date: Mon, 23 Mar 2026 11:38:36 -0700 Message-ID: <20260323183844.3146982-12-joe@dama.to> X-Mailer: git-send-email 2.52.0 In-Reply-To: <20260323183844.3146982-1-joe@dama.to> References: <20260323183844.3146982-1-joe@dama.to> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Add support for UDP Segmentation Offloading in software (SW USO). This is helpful for testing when real hardware is not available. A test which uses this codepath will be added in a following commit. Suggested-by: Jakub Kicinski Reviewed-by: Pavan Chebbi Signed-off-by: Joe Damato --- v5: - Added Pavan's Reviewed-by. No functional changes. v4: - Added parentheses around the gso_type check for clarity. No functional change. rfcv2: - new in rfcv2 drivers/net/netdevsim/netdev.c | 100 ++++++++++++++++++++++++++++++++- 1 file changed, 99 insertions(+), 1 deletion(-) diff --git a/drivers/net/netdevsim/netdev.c b/drivers/net/netdevsim/netdev.c index c71b8d116f18..f228bcf3d190 100644 --- a/drivers/net/netdevsim/netdev.c +++ b/drivers/net/netdevsim/netdev.c @@ -30,6 +30,7 @@ #include #include #include +#include #include "netdevsim.h" @@ -120,6 +121,98 @@ static int nsim_forward_skb(struct net_device *tx_dev, return nsim_napi_rx(tx_dev, rx_dev, rq, skb); } +static netdev_tx_t nsim_uso_segment_xmit(struct net_device *dev, + struct sk_buff *skb) +{ + unsigned int hdr_len, mss, total_payload, num_segs; + struct netdevsim *ns = netdev_priv(dev); + struct net_device *peer_dev; + unsigned int total_len = 0; + struct netdevsim *peer_ns; + struct nsim_rq *rq; + struct tso_t tso; + int i, rxq; + + hdr_len = tso_start(skb, &tso); + mss = skb_shinfo(skb)->gso_size; + total_payload = skb->len - hdr_len; + num_segs = DIV_ROUND_UP(total_payload, mss); + + udp_hdr(skb)->check = 0; + if (!tso.ipv6) + ip_hdr(skb)->check = 0; + + rcu_read_lock(); + peer_ns = rcu_dereference(ns->peer); + if (!peer_ns) + goto out_drop_free; + + peer_dev = peer_ns->netdev; + rxq = skb_get_queue_mapping(skb); + if (rxq >= peer_dev->num_rx_queues) + rxq = rxq % peer_dev->num_rx_queues; + rq = peer_ns->rq[rxq]; + + for (i = 0; i < num_segs; i++) { + unsigned int seg_payload = min_t(unsigned int, mss, + total_payload); + bool last = (i == num_segs - 1); + unsigned int seg_remaining; + struct sk_buff *seg; + + seg = alloc_skb(hdr_len + seg_payload, GFP_ATOMIC); + if (!seg) + break; + + seg->dev = dev; + + tso_build_hdr(skb, skb_put(seg, hdr_len), &tso, + seg_payload, last); + + if (!tso.ipv6) { + unsigned int nh_off = skb_network_offset(skb); + struct iphdr *iph; + + iph = (struct iphdr *)(seg->data + nh_off); + iph->check = ip_fast_csum(iph, iph->ihl); + } + + seg_remaining = seg_payload; + while (seg_remaining > 0) { + unsigned int chunk = min_t(unsigned int, tso.size, + seg_remaining); + + memcpy(skb_put(seg, chunk), tso.data, chunk); + tso_build_data(skb, &tso, chunk); + seg_remaining -= chunk; + } + + total_payload -= seg_payload; + + seg->ip_summed = CHECKSUM_UNNECESSARY; + + if (nsim_forward_skb(dev, peer_dev, seg, rq, NULL) == NET_RX_DROP) + continue; + + total_len += hdr_len + seg_payload; + } + + if (!hrtimer_active(&rq->napi_timer)) + hrtimer_start(&rq->napi_timer, us_to_ktime(5), + HRTIMER_MODE_REL); + + rcu_read_unlock(); + dev_kfree_skb(skb); + dev_dstats_tx_add(dev, total_len); + return NETDEV_TX_OK; + +out_drop_free: + dev_kfree_skb(skb); + rcu_read_unlock(); + dev_dstats_tx_dropped(dev); + return NETDEV_TX_OK; +} + static netdev_tx_t nsim_start_xmit(struct sk_buff *skb, struct net_device *dev) { struct netdevsim *ns = netdev_priv(dev); @@ -132,6 +225,10 @@ static netdev_tx_t nsim_start_xmit(struct sk_buff *skb, struct net_device *dev) int rxq; int dr; + if (skb_is_gso(skb) && + skb_shinfo(skb)->gso_type & SKB_GSO_UDP_L4) + return nsim_uso_segment_xmit(dev, skb); + rcu_read_lock(); if (!nsim_ipsec_tx(ns, skb)) goto out_drop_any; @@ -938,7 +1035,8 @@ static void nsim_setup(struct net_device *dev) NETIF_F_HW_CSUM | NETIF_F_LRO | NETIF_F_TSO | - NETIF_F_LOOPBACK; + NETIF_F_LOOPBACK | + NETIF_F_GSO_UDP_L4; dev->pcpu_stat_type = NETDEV_PCPU_STAT_DSTATS; dev->max_mtu = ETH_MAX_MTU; dev->xdp_features = NETDEV_XDP_ACT_BASIC | NETDEV_XDP_ACT_HW_OFFLOAD; -- 2.52.0