netdev - [PATCH net-next] xdp: add multi-buff support for xdp running in generic mode

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Message-ID: <c928f7c698de070b33d38f230081fd4f993f2567.1701128026.git.lorenzo@kernel.org>
Date: Tue, 28 Nov 2023 00:38:32 +0100
From: Lorenzo Bianconi <lorenzo@...nel.org>
To: netdev@...r.kernel.org
Cc: davem@...emloft.net,
	edumazet@...gle.com,
	kuba@...nel.org,
	pabeni@...hat.com,
	lorenzo.bianconi@...hat.com,
	bpf@...r.kernel.org,
	hawk@...nel.org,
	toke@...hat.com
Subject: [PATCH net-next] xdp: add multi-buff support for xdp running in generic mode

Similar to native xdp, do not always linearize the skb in
netif_receive_generic_xdp routine but create a non-linear xdp_buff to be
processed by the eBPF program. This allow to add multi-buffer support
for xdp running in generic mode.

Signed-off-by: Lorenzo Bianconi <lorenzo@...nel.org>
---
 net/core/dev.c | 28 +++++++++++++++++++++++-----
 1 file changed, 23 insertions(+), 5 deletions(-)

diff --git a/net/core/dev.c b/net/core/dev.c
index 3950ced396b5..5a58f3e28657 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -4853,6 +4853,12 @@ u32 bpf_prog_run_generic_xdp(struct sk_buff *skb, struct xdp_buff *xdp,
 	xdp_init_buff(xdp, frame_sz, &rxqueue->xdp_rxq);
 	xdp_prepare_buff(xdp, hard_start, skb_headroom(skb) - mac_len,
 			 skb_headlen(skb) + mac_len, true);
+	if (skb_is_nonlinear(skb)) {
+		skb_shinfo(skb)->xdp_frags_size = skb->data_len;
+		xdp_buff_set_frags_flag(xdp);
+	} else {
+		xdp_buff_clear_frags_flag(xdp);
+	}
 
 	orig_data_end = xdp->data_end;
 	orig_data = xdp->data;
@@ -4882,6 +4888,14 @@ u32 bpf_prog_run_generic_xdp(struct sk_buff *skb, struct xdp_buff *xdp,
 		skb->len += off; /* positive on grow, negative on shrink */
 	}
 
+	/* XDP frag metadata (e.g. nr_frags) are updated in eBPF helpers
+	 * (e.g. bpf_xdp_adjust_tail), we need to update data_len here.
+	 */
+	if (xdp_buff_has_frags(xdp))
+		skb->data_len = skb_shinfo(skb)->xdp_frags_size;
+	else
+		skb->data_len = 0;
+
 	/* check if XDP changed eth hdr such SKB needs update */
 	eth = (struct ethhdr *)xdp->data;
 	if ((orig_eth_type != eth->h_proto) ||
@@ -4927,9 +4941,9 @@ static u32 netif_receive_generic_xdp(struct sk_buff *skb,
 	if (skb_is_redirected(skb))
 		return XDP_PASS;
 
-	/* XDP packets must be linear and must have sufficient headroom
-	 * of XDP_PACKET_HEADROOM bytes. This is the guarantee that also
-	 * native XDP provides, thus we need to do it here as well.
+	/* XDP packets must have sufficient headroom of XDP_PACKET_HEADROOM
+	 * bytes. This is the guarantee that also native XDP provides,
+	 * thus we need to do it here as well.
 	 */
 	if (skb_cloned(skb) || skb_is_nonlinear(skb) ||
 	    skb_headroom(skb) < XDP_PACKET_HEADROOM) {
@@ -4943,8 +4957,12 @@ static u32 netif_receive_generic_xdp(struct sk_buff *skb,
 				     hroom > 0 ? ALIGN(hroom, NET_SKB_PAD) : 0,
 				     troom > 0 ? troom + 128 : 0, GFP_ATOMIC))
 			goto do_drop;
-		if (skb_linearize(skb))
-			goto do_drop;
+
+		/* XDP does not support fraglist */
+		if (skb_has_frag_list(skb) || !xdp_prog->aux->xdp_has_frags) {
+			if (skb_linearize(skb))
+				goto do_drop;
+		}
 	}
 
 	act = bpf_prog_run_generic_xdp(skb, xdp, xdp_prog);
-- 
2.43.0