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Message-Id: <20250925160009.2474816-4-maciej.fijalkowski@intel.com>
Date: Thu, 25 Sep 2025 18:00:09 +0200
From: Maciej Fijalkowski <maciej.fijalkowski@...el.com>
To: bpf@...r.kernel.org,
ast@...nel.org,
daniel@...earbox.net,
andrii@...nel.org
Cc: netdev@...r.kernel.org,
magnus.karlsson@...el.com,
stfomichev@...il.com,
kerneljasonxing@...il.com,
Maciej Fijalkowski <maciej.fijalkowski@...el.com>,
Stanislav Fomichev <sdf@...ichev.me>
Subject: [PATCH v2 bpf-next 3/3] xsk: wrap generic metadata handling onto separate function
xsk_build_skb() has gone wild with its size and one of the things we can
do about it is to pull out a branch that takes care of metadata handling
and make it a separate function.
While at it, let us add metadata SW support for devices supporting
IFF_TX_SKB_NO_LINEAR flag, that happen to have separate logic for
building skb in xsk's generic xmit path.
Acked-by: Stanislav Fomichev <sdf@...ichev.me>
Reviewed-by: Jason Xing <kerneljasonxing@...il.com>
Signed-off-by: Maciej Fijalkowski <maciej.fijalkowski@...el.com>
---
net/xdp/xsk.c | 92 +++++++++++++++++++++++++++++----------------------
1 file changed, 53 insertions(+), 39 deletions(-)
diff --git a/net/xdp/xsk.c b/net/xdp/xsk.c
index f7e0d254a723..7b0c68a70888 100644
--- a/net/xdp/xsk.c
+++ b/net/xdp/xsk.c
@@ -657,6 +657,45 @@ static void xsk_drop_skb(struct sk_buff *skb)
xsk_consume_skb(skb);
}
+static int xsk_skb_metadata(struct sk_buff *skb, void *buffer,
+ struct xdp_desc *desc, struct xsk_buff_pool *pool,
+ u32 hr)
+{
+ struct xsk_tx_metadata *meta = NULL;
+
+ if (unlikely(pool->tx_metadata_len == 0))
+ return -EINVAL;
+
+ meta = buffer - pool->tx_metadata_len;
+ if (unlikely(!xsk_buff_valid_tx_metadata(meta)))
+ return -EINVAL;
+
+ if (meta->flags & XDP_TXMD_FLAGS_CHECKSUM) {
+ if (unlikely(meta->request.csum_start +
+ meta->request.csum_offset +
+ sizeof(__sum16) > desc->len))
+ return -EINVAL;
+
+ skb->csum_start = hr + meta->request.csum_start;
+ skb->csum_offset = meta->request.csum_offset;
+ skb->ip_summed = CHECKSUM_PARTIAL;
+
+ if (unlikely(pool->tx_sw_csum)) {
+ int err;
+
+ err = skb_checksum_help(skb);
+ if (err)
+ return err;
+ }
+ }
+
+ if (meta->flags & XDP_TXMD_FLAGS_LAUNCH_TIME)
+ skb->skb_mstamp_ns = meta->request.launch_time;
+ xsk_tx_metadata_to_compl(meta, &skb_shinfo(skb)->xsk_meta);
+
+ return 0;
+}
+
static struct sk_buff *xsk_build_skb_zerocopy(struct xdp_sock *xs,
struct xdp_desc *desc)
{
@@ -669,6 +708,9 @@ static struct sk_buff *xsk_build_skb_zerocopy(struct xdp_sock *xs,
int err, i;
u64 addr;
+ addr = desc->addr;
+ buffer = xsk_buff_raw_get_data(pool, addr);
+
if (!skb) {
hr = max(NET_SKB_PAD, L1_CACHE_ALIGN(xs->dev->needed_headroom));
@@ -679,6 +721,11 @@ static struct sk_buff *xsk_build_skb_zerocopy(struct xdp_sock *xs,
skb_reserve(skb, hr);
xsk_skb_init_misc(skb, xs, desc->addr);
+ if (desc->options & XDP_TX_METADATA) {
+ err = xsk_skb_metadata(skb, buffer, desc, pool, hr);
+ if (unlikely(err))
+ return ERR_PTR(err);
+ }
} else {
xsk_addr = kmem_cache_zalloc(xsk_tx_generic_cache, GFP_KERNEL);
if (!xsk_addr)
@@ -692,11 +739,9 @@ static struct sk_buff *xsk_build_skb_zerocopy(struct xdp_sock *xs,
list_add_tail(&xsk_addr->addr_node, &XSKCB(skb)->addrs_list);
}
- addr = desc->addr;
len = desc->len;
ts = pool->unaligned ? len : pool->chunk_size;
- buffer = xsk_buff_raw_get_data(pool, addr);
offset = offset_in_page(buffer);
addr = buffer - pool->addrs;
@@ -727,7 +772,6 @@ static struct sk_buff *xsk_build_skb_zerocopy(struct xdp_sock *xs,
static struct sk_buff *xsk_build_skb(struct xdp_sock *xs,
struct xdp_desc *desc)
{
- struct xsk_tx_metadata *meta = NULL;
struct net_device *dev = xs->dev;
struct sk_buff *skb = xs->skb;
int err;
@@ -761,6 +805,12 @@ static struct sk_buff *xsk_build_skb(struct xdp_sock *xs,
goto free_err;
xsk_skb_init_misc(skb, xs, desc->addr);
+ if (desc->options & XDP_TX_METADATA) {
+ err = xsk_skb_metadata(skb, buffer, desc,
+ xs->pool, hr);
+ if (unlikely(err))
+ goto free_err;
+ }
} else {
int nr_frags = skb_shinfo(skb)->nr_frags;
struct xsk_addr_node *xsk_addr;
@@ -795,42 +845,6 @@ static struct sk_buff *xsk_build_skb(struct xdp_sock *xs,
xsk_addr->addr = desc->addr;
list_add_tail(&xsk_addr->addr_node, &XSKCB(skb)->addrs_list);
}
-
- if (!skb_shinfo(skb)->nr_frags && desc->options & XDP_TX_METADATA) {
- if (unlikely(xs->pool->tx_metadata_len == 0)) {
- err = -EINVAL;
- goto free_err;
- }
-
- meta = buffer - xs->pool->tx_metadata_len;
- if (unlikely(!xsk_buff_valid_tx_metadata(meta))) {
- err = -EINVAL;
- goto free_err;
- }
-
- if (meta->flags & XDP_TXMD_FLAGS_CHECKSUM) {
- if (unlikely(meta->request.csum_start +
- meta->request.csum_offset +
- sizeof(__sum16) > len)) {
- err = -EINVAL;
- goto free_err;
- }
-
- skb->csum_start = hr + meta->request.csum_start;
- skb->csum_offset = meta->request.csum_offset;
- skb->ip_summed = CHECKSUM_PARTIAL;
-
- if (unlikely(xs->pool->tx_sw_csum)) {
- err = skb_checksum_help(skb);
- if (err)
- goto free_err;
- }
- }
-
- if (meta->flags & XDP_TXMD_FLAGS_LAUNCH_TIME)
- skb->skb_mstamp_ns = meta->request.launch_time;
- xsk_tx_metadata_to_compl(meta, &skb_shinfo(skb)->xsk_meta);
- }
}
xsk_inc_num_desc(skb);
--
2.43.0
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