这应该就是 kernel network 的会议吧

每一次的开会都是在 youtube 上搜索到的

netdev 的 features 列举

Documentation/networking/netdev-features.rst

 * Transmit UDP segmentation offload

NETIF_F_GSO_UDP_L4 accepts a single UDP header with a payload that exceeds
gso_size. On segmentation, it segments the payload on gso_size boundaries and
replicates the network and UDP headers (fixing up the last one if less than
gso_size).

什么问题?

NETIF_F_GSO_UDP NETIF_F_GSO_UDP_L4

I’ll try testing this out, but preliminarily, NETIF_F_GSO_SOFTWARE already contains NETIF_F_GSO_UDP_L4.

And as far as my understanding goes, NETIF_F_GSO_UDP is deprecated for all use, except for tuntap. So, we probably shouldn’t add it. UFO generally creates more issues than it solves.

不太可以增加:

/* List of features with software fallbacks. */
#define NETIF_F_GSO_SOFTWARE	(NETIF_F_ALL_TSO | NETIF_F_GSO_SCTP |	     \
				 NETIF_F_GSO_UDP_L4 | NETIF_F_GSO_FRAGLIST)

enum {
  // ...
	NETIF_F_GSO_UDP_BIT,		/* ... UFO, deprecated except tuntap */
	NETIF_F_GSO_UDP_L4_BIT,		/* ... UDP payload GSO (not UFO) */

NETIF_F_GSO_UDP 的确是没有 reference 了!

History:        #0
Commit:         2e4ef10f58502323ea470bc30ba84d5ddd4e77f0
Author:         Alexander Lobakin <alobakin@pm.me>
Committer:      Jakub Kicinski <kuba@kernel.org>
Author Date:    Sun 01 Nov 2020 09:17:07 PM CST
Committer Date: Wed 04 Nov 2020 08:53:55 AM CST

net: add GSO UDP L4 and GSO fraglists to the list of software-backed types

Commit e20cf8d3f1f7 ("udp: implement GRO for plain UDP sockets.") and
commit 9fd1ff5d2ac7 ("udp: Support UDP fraglist GRO/GSO.") made UDP L4
and fraglisted GRO/GSO fully supported by the software fallback mode.
We can safely add them to NETIF_F_GSO_SOFTWARE to allow logical/virtual
netdevs to forward these types of skbs up to the real drivers.

Signed-off-by: Alexander Lobakin <alobakin@pm.me>
Acked-by: Willem de Bruijn <willemb@google.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/include/linux/netdev_features.h b/include/linux/netdev_features.h
index 0b17c4322b09..934de56644e7 100644
--- a/include/linux/netdev_features.h
+++ b/include/linux/netdev_features.h
@@ -207,8 +207,8 @@ static inline int find_next_netdev_feature(u64 feature, unsigned long start)
 				 NETIF_F_FSO)

 /* List of features with software fallbacks. */
-#define NETIF_F_GSO_SOFTWARE	(NETIF_F_ALL_TSO | \
-				 NETIF_F_GSO_SCTP)
+#define NETIF_F_GSO_SOFTWARE	(NETIF_F_ALL_TSO | NETIF_F_GSO_SCTP |	     \
+				 NETIF_F_GSO_UDP_L4 | NETIF_F_GSO_FRAGLIST)

 /*
  * If one device supports one of these features, then enable them

gso: fix dodgy bit handling for GSO_UDP_L4

History:        #0
Commit:         9840036786d90cea11a90d1f30b6dc003b34ee67
Author:         Yan Zhai <yan@cloudflare.com>
Committer:      David S. Miller <davem@davemloft.net>
Author Date:    Fri 14 Jul 2023 01:28:00 AM CST
Committer Date: Fri 14 Jul 2023 05:29:20 PM CST

gso: fix dodgy bit handling for GSO_UDP_L4

Commit 1fd54773c267 ("udp: allow header check for dodgy GSO_UDP_L4
packets.") checks DODGY bit for UDP, but for packets that can be fed
directly to the device after gso_segs reset, it actually falls through
to fragmentation:

https://lore.kernel.org/all/CAJPywTKDdjtwkLVUW6LRA2FU912qcDmQOQGt2WaDo28KzYDg+A@mail.gmail.com/

This change restores the expected behavior of GSO_UDP_L4 packets.

Fixes: 1fd54773c267 ("udp: allow header check for dodgy GSO_UDP_L4 packets.")
Suggested-by: Willem de Bruijn <willemdebruijn.kernel@gmail.com>
Signed-off-by: Yan Zhai <yan@cloudflare.com>
Reviewed-by: Willem de Bruijn <willemb@google.com>
Acked-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/ipv4/udp_offload.c b/net/ipv4/udp_offload.c
index 75aa4de5b731..f402946da344 100644
--- a/net/ipv4/udp_offload.c
+++ b/net/ipv4/udp_offload.c
@@ -274,13 +274,20 @@ struct sk_buff *__udp_gso_segment(struct sk_buff *gso_skb,
 	__sum16 check;
 	__be16 newlen;

-	if (skb_shinfo(gso_skb)->gso_type & SKB_GSO_FRAGLIST)
-		return __udp_gso_segment_list(gso_skb, features, is_ipv6);
-
 	mss = skb_shinfo(gso_skb)->gso_size;
 	if (gso_skb->len <= sizeof(*uh) + mss)
 		return ERR_PTR(-EINVAL);

+	if (skb_gso_ok(gso_skb, features | NETIF_F_GSO_ROBUST)) {
+		/* Packet is from an untrusted source, reset gso_segs. */
+		skb_shinfo(gso_skb)->gso_segs = DIV_ROUND_UP(gso_skb->len - sizeof(*uh),
+							     mss);
+		return NULL;
+	}
+
+	if (skb_shinfo(gso_skb)->gso_type & SKB_GSO_FRAGLIST)
+		return __udp_gso_segment_list(gso_skb, features, is_ipv6);
+
 	skb_pull(gso_skb, sizeof(*uh));

 	/* clear destructor to avoid skb_segment assigning it to tail */
@@ -388,8 +395,7 @@ static struct sk_buff *udp4_ufo_fragment(struct sk_buff *skb,
 	if (!pskb_may_pull(skb, sizeof(struct udphdr)))
 		goto out;

-	if (skb_shinfo(skb)->gso_type & SKB_GSO_UDP_L4 &&
-	    !skb_gso_ok(skb, features | NETIF_F_GSO_ROBUST))
+	if (skb_shinfo(skb)->gso_type & SKB_GSO_UDP_L4)
 		return __udp_gso_segment(skb, features, false);

 	mss = skb_shinfo(skb)->gso_size;

NETIF_F_GSO_ROBUST 是 GSO 的一部分吧

https://lore.kernel.org/netdev/20220907125048.396126-2-andrew@daynix.com/

[ ] UFO 不支持了?

GSO 有这么多的 type 啊

enum {
	SKB_GSO_TCPV4 = 1 << 0,

	/* This indicates the skb is from an untrusted source. */
	SKB_GSO_DODGY = 1 << 1,

	/* This indicates the tcp segment has CWR set. */
	SKB_GSO_TCP_ECN = 1 << 2,

	SKB_GSO_TCP_FIXEDID = 1 << 3,

	SKB_GSO_TCPV6 = 1 << 4,

	SKB_GSO_FCOE = 1 << 5,

	SKB_GSO_GRE = 1 << 6,

	SKB_GSO_GRE_CSUM = 1 << 7,

	SKB_GSO_IPXIP4 = 1 << 8,

	SKB_GSO_IPXIP6 = 1 << 9,

	SKB_GSO_UDP_TUNNEL = 1 << 10,

	SKB_GSO_UDP_TUNNEL_CSUM = 1 << 11,

	SKB_GSO_PARTIAL = 1 << 12,

	SKB_GSO_TUNNEL_REMCSUM = 1 << 13,

	SKB_GSO_SCTP = 1 << 14,

	SKB_GSO_ESP = 1 << 15,

	SKB_GSO_UDP = 1 << 16,

	SKB_GSO_UDP_L4 = 1 << 17,

	SKB_GSO_FRAGLIST = 1 << 18,
};

ethtool -k 可以检查网卡的特性

可以看到，的确是非常不一样的:

wg0 : wireguard 网卡

➜  ~  ethtool -k wg0
Features for wg0:
rx-checksumming: on
tx-checksumming: on
        tx-checksum-ipv4: off [fixed]
        tx-checksum-ip-generic: on
        tx-checksum-ipv6: off [fixed]
        tx-checksum-fcoe-crc: off [fixed]
        tx-checksum-sctp: off [fixed]
scatter-gather: on
        tx-scatter-gather: on
        tx-scatter-gather-fraglist: off [fixed]
tcp-segmentation-offload: on
        tx-tcp-segmentation: on
        tx-tcp-ecn-segmentation: on
        tx-tcp-mangleid-segmentation: on
        tx-tcp6-segmentation: on
generic-segmentation-offload: on
generic-receive-offload: on
large-receive-offload: off [fixed]
rx-vlan-offload: off [fixed]
tx-vlan-offload: off [fixed]
ntuple-filters: off [fixed]
receive-hashing: off [fixed]
highdma: on
rx-vlan-filter: off [fixed]
vlan-challenged: off [fixed]
tx-lockless: on [fixed]
netns-local: off [fixed]
tx-gso-robust: off [fixed]
tx-fcoe-segmentation: off [fixed]
tx-gre-segmentation: off [fixed]
tx-gre-csum-segmentation: off [fixed]
tx-ipxip4-segmentation: off [fixed]
tx-ipxip6-segmentation: off [fixed]
tx-udp_tnl-segmentation: off [fixed]
tx-udp_tnl-csum-segmentation: off [fixed]
tx-gso-partial: off [fixed]
tx-tunnel-remcsum-segmentation: off [fixed]
tx-sctp-segmentation: on
tx-esp-segmentation: off [fixed]
tx-udp-segmentation: on
tx-gso-list: on
fcoe-mtu: off [fixed]
tx-nocache-copy: off
loopback: off [fixed]
rx-fcs: off [fixed]
rx-all: off [fixed]
tx-vlan-stag-hw-insert: off [fixed]
rx-vlan-stag-hw-parse: off [fixed]
rx-vlan-stag-filter: off [fixed]
l2-fwd-offload: off [fixed]
hw-tc-offload: off [fixed]
esp-hw-offload: off [fixed]
esp-tx-csum-hw-offload: off [fixed]
rx-udp_tunnel-port-offload: off [fixed]
tls-hw-tx-offload: off [fixed]
tls-hw-rx-offload: off [fixed]
rx-gro-hw: off [fixed]
tls-hw-record: off [fixed]
rx-gro-list: off
macsec-hw-offload: off [fixed]
rx-udp-gro-forwarding: off
hsr-tag-ins-offload: off [fixed]
hsr-tag-rm-offload: off [fixed]
hsr-fwd-offload: off [fixed]
hsr-dup-offload: off [fixed]

ens6 : virtio 网卡

➜  ~  ethtool -k ens6
Features for ens6:
rx-checksumming: on [fixed]
tx-checksumming: on
        tx-checksum-ipv4: off [fixed]
        tx-checksum-ip-generic: on
        tx-checksum-ipv6: off [fixed]
        tx-checksum-fcoe-crc: off [fixed]
        tx-checksum-sctp: off [fixed]
scatter-gather: on
        tx-scatter-gather: on
        tx-scatter-gather-fraglist: off [fixed]
tcp-segmentation-offload: on
        tx-tcp-segmentation: on
        tx-tcp-ecn-segmentation: on
        tx-tcp-mangleid-segmentation: off
        tx-tcp6-segmentation: on
generic-segmentation-offload: on
generic-receive-offload: on
large-receive-offload: off [fixed]
rx-vlan-offload: off [fixed]
tx-vlan-offload: off [fixed]
ntuple-filters: off [fixed]
receive-hashing: off [fixed]
highdma: on [fixed]
rx-vlan-filter: on [fixed]
vlan-challenged: off [fixed]
tx-lockless: off [fixed]
netns-local: off [fixed]
tx-gso-robust: on [fixed]
tx-fcoe-segmentation: off [fixed]
tx-gre-segmentation: off [fixed]
tx-gre-csum-segmentation: off [fixed]
tx-ipxip4-segmentation: off [fixed]
tx-ipxip6-segmentation: off [fixed]
tx-udp_tnl-segmentation: off [fixed]
tx-udp_tnl-csum-segmentation: off [fixed]
tx-gso-partial: off [fixed]
tx-tunnel-remcsum-segmentation: off [fixed]
tx-sctp-segmentation: off [fixed]
tx-esp-segmentation: off [fixed]
tx-udp-segmentation: off
tx-gso-list: off [fixed]
fcoe-mtu: off [fixed]
tx-nocache-copy: off
loopback: off [fixed]
rx-fcs: off [fixed]
rx-all: off [fixed]
tx-vlan-stag-hw-insert: off [fixed]
rx-vlan-stag-hw-parse: off [fixed]
rx-vlan-stag-filter: off [fixed]
l2-fwd-offload: off [fixed]
hw-tc-offload: off [fixed]
esp-hw-offload: off [fixed]
esp-tx-csum-hw-offload: off [fixed]
rx-udp_tunnel-port-offload: off [fixed]
tls-hw-tx-offload: off [fixed]
tls-hw-rx-offload: off [fixed]
rx-gro-hw: on
tls-hw-record: off [fixed]
rx-gro-list: off
macsec-hw-offload: off [fixed]
rx-udp-gro-forwarding: off
hsr-tag-ins-offload: off [fixed]
hsr-tag-rm-offload: off [fixed]
hsr-fwd-offload: off [fixed]
hsr-dup-offload: off [fixed]

#define VIRTNET_FEATURES \
	VIRTIO_NET_F_CSUM, VIRTIO_NET_F_GUEST_CSUM, \
	VIRTIO_NET_F_MAC, \
	VIRTIO_NET_F_HOST_TSO4, VIRTIO_NET_F_HOST_UFO, VIRTIO_NET_F_HOST_TSO6, \
	VIRTIO_NET_F_HOST_ECN, VIRTIO_NET_F_GUEST_TSO4, VIRTIO_NET_F_GUEST_TSO6, \
	VIRTIO_NET_F_GUEST_ECN, VIRTIO_NET_F_GUEST_UFO, \
	VIRTIO_NET_F_HOST_USO, VIRTIO_NET_F_GUEST_USO4, VIRTIO_NET_F_GUEST_USO6, \
	VIRTIO_NET_F_MRG_RXBUF, VIRTIO_NET_F_STATUS, VIRTIO_NET_F_CTRL_VQ, \
	VIRTIO_NET_F_CTRL_RX, VIRTIO_NET_F_CTRL_VLAN, \
	VIRTIO_NET_F_GUEST_ANNOUNCE, VIRTIO_NET_F_MQ, \
	VIRTIO_NET_F_CTRL_MAC_ADDR, \
	VIRTIO_NET_F_MTU, VIRTIO_NET_F_CTRL_GUEST_OFFLOADS, \
	VIRTIO_NET_F_SPEED_DUPLEX, VIRTIO_NET_F_STANDBY, \
	VIRTIO_NET_F_RSS, VIRTIO_NET_F_HASH_REPORT, VIRTIO_NET_F_NOTF_COAL, \
	VIRTIO_NET_F_VQ_NOTF_COAL, \
	VIRTIO_NET_F_GUEST_HDRLEN

static unsigned int features[] = {
	VIRTNET_FEATURES,
};

static unsigned int features_legacy[] = {
	VIRTNET_FEATURES,
	VIRTIO_NET_F_GSO,
	VIRTIO_F_ANY_LAYOUT,
};

似乎是在 virtnet_probe 中协商的

ens9 : 直通的网卡

➜  ~ ethtool -k ens9
Features for ens9:
rx-checksumming: on
tx-checksumming: on
        tx-checksum-ipv4: off [fixed]
        tx-checksum-ip-generic: on
        tx-checksum-ipv6: off [fixed]
        tx-checksum-fcoe-crc: off [fixed]
        tx-checksum-sctp: on
scatter-gather: on
        tx-scatter-gather: on
        tx-scatter-gather-fraglist: off [fixed]
tcp-segmentation-offload: on
        tx-tcp-segmentation: on
        tx-tcp-ecn-segmentation: on
        tx-tcp-mangleid-segmentation: off
        tx-tcp6-segmentation: on
generic-segmentation-offload: on
generic-receive-offload: on
large-receive-offload: off [fixed]
rx-vlan-offload: off
tx-vlan-offload: off
ntuple-filters: off
receive-hashing: on
highdma: on [fixed]
rx-vlan-filter: off [fixed]
vlan-challenged: off [fixed]
tx-lockless: off [fixed]
netns-local: off [fixed]
tx-gso-robust: off [fixed]
tx-fcoe-segmentation: off [fixed]
tx-gre-segmentation: on
tx-gre-csum-segmentation: on
tx-ipxip4-segmentation: on
tx-ipxip6-segmentation: on
tx-udp_tnl-segmentation: on
tx-udp_tnl-csum-segmentation: on
tx-gso-partial: on
tx-tunnel-remcsum-segmentation: off [fixed]
tx-sctp-segmentation: off [fixed]
tx-esp-segmentation: off [fixed]
tx-udp-segmentation: off [fixed]
tx-gso-list: off [fixed]
fcoe-mtu: off [fixed]
tx-nocache-copy: off
loopback: off [fixed]
rx-fcs: off [fixed]
rx-all: off [fixed]
tx-vlan-stag-hw-insert: off [fixed]
rx-vlan-stag-hw-parse: off [fixed]
rx-vlan-stag-filter: off [fixed]
l2-fwd-offload: off [fixed]
hw-tc-offload: on
esp-hw-offload: off [fixed]
esp-tx-csum-hw-offload: off [fixed]
rx-udp_tunnel-port-offload: off [fixed]
tls-hw-tx-offload: off [fixed]
tls-hw-rx-offload: off [fixed]
rx-gro-hw: off [fixed]
tls-hw-record: off [fixed]
rx-gro-list: off
macsec-hw-offload: off [fixed]
rx-udp-gro-forwarding: off
hsr-tag-ins-offload: off [fixed]
hsr-tag-rm-offload: off [fixed]
hsr-fwd-offload: off [fixed]
hsr-dup-offload: off [fixed]

原来可以动态关闭的

ethtoo -K eth0 ufo off

如果将 ufo 关闭，那么 guest os 不会发送大的包!

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