openwrt/target/linux/generic/backport-6.6/611-01-v6.11-udp-Allow-GSO-transmit-from-devices-with-no-checksum.patch
John Audia 28f534d953
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kernel: bump 6.6 to 6.6.66
Update patch set for new release and add required kernel option
CONFIG_ZRAM_TRACK_ENTRY_ACTIME to generic config

Changelog: https://cdn.kernel.org/pub/linux/kernel/v6.x/ChangeLog-6.6.66

Manually rebased:
	bcm27xx/patches-6.6/950-0092-MMC-added-alternative-MMC-driver.patch
	bcm53xx/patches-6.6/180-usb-xhci-add-support-for-performing-fake-doorbell.patch
	starfive/patches-6.6/1000-serial-8250_dw-Add-starfive-jh7100-hsuart-compatible.patch

Removed upstreamed:
	bcm27xx/patches-6.6/950-0029-vc4_hdmi-Avoid-log-spam-for-audio-start-failure.patch[1]

All other patches automatically rebased.

1. https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?h=v6.6.66&id=e0388a95736abd1f5f5a94221dd1ac24eacbd4d7

Build system: x86/64
Build-tested: bcm27xx/bcm2712, flogic/glinet_gl-mt6000, flogic/xiaomi_redmi-router-ax6000-ubootmod, ramips/tplink_archer-a6-v3, x86/64
Run-tested: bcm27xx/bcm2712, flogic/glinet_gl-mt6000, flogic/xiaomi_redmi-router-ax6000-ubootmod, ramips/tplink_archer-a6-v3, x86/64

Signed-off-by: John Audia <therealgraysky@proton.me>
Link: https://github.com/openwrt/openwrt/pull/17271
Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>
2024-12-19 00:38:34 +01:00

95 lines
3.4 KiB
Diff

From: Jakub Sitnicki <jakub@cloudflare.com>
Date: Wed, 26 Jun 2024 19:51:26 +0200
Subject: [PATCH] udp: Allow GSO transmit from devices with no checksum offload
Today sending a UDP GSO packet from a TUN device results in an EIO error:
import fcntl, os, struct
from socket import *
TUNSETIFF = 0x400454CA
IFF_TUN = 0x0001
IFF_NO_PI = 0x1000
UDP_SEGMENT = 103
tun_fd = os.open("/dev/net/tun", os.O_RDWR)
ifr = struct.pack("16sH", b"tun0", IFF_TUN | IFF_NO_PI)
fcntl.ioctl(tun_fd, TUNSETIFF, ifr)
os.system("ip addr add 192.0.2.1/24 dev tun0")
os.system("ip link set dev tun0 up")
s = socket(AF_INET, SOCK_DGRAM)
s.setsockopt(SOL_UDP, UDP_SEGMENT, 1200)
s.sendto(b"x" * 3000, ("192.0.2.2", 9)) # EIO
This is due to a check in the udp stack if the egress device offers
checksum offload. While TUN/TAP devices, by default, don't advertise this
capability because it requires support from the TUN/TAP reader.
However, the GSO stack has a software fallback for checksum calculation,
which we can use. This way we don't force UDP_SEGMENT users to handle the
EIO error and implement a segmentation fallback.
Lift the restriction so that UDP_SEGMENT can be used with any egress
device. We also need to adjust the UDP GSO code to match the GSO stack
expectation about ip_summed field, as set in commit 8d63bee643f1 ("net:
avoid skb_warn_bad_offload false positives on UFO"). Otherwise we will hit
the bad offload check.
Users should, however, expect a potential performance impact when
batch-sending packets with UDP_SEGMENT without checksum offload on the
egress device. In such case the packet payload is read twice: first during
the sendmsg syscall when copying data from user memory, and then in the GSO
stack for checksum computation. This double memory read can be less
efficient than a regular sendmsg where the checksum is calculated during
the initial data copy from user memory.
Signed-off-by: Jakub Sitnicki <jakub@cloudflare.com>
Reviewed-by: Willem de Bruijn <willemb@google.com>
Link: https://patch.msgid.link/20240626-linux-udpgso-v2-1-422dfcbd6b48@cloudflare.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
---
--- a/net/ipv4/udp.c
+++ b/net/ipv4/udp.c
@@ -942,8 +942,7 @@ static int udp_send_skb(struct sk_buff *
kfree_skb(skb);
return -EINVAL;
}
- if (skb->ip_summed != CHECKSUM_PARTIAL || is_udplite ||
- dst_xfrm(skb_dst(skb))) {
+ if (is_udplite || dst_xfrm(skb_dst(skb))) {
kfree_skb(skb);
return -EIO;
}
--- a/net/ipv4/udp_offload.c
+++ b/net/ipv4/udp_offload.c
@@ -380,6 +380,14 @@ struct sk_buff *__udp_gso_segment(struct
else
uh->check = gso_make_checksum(seg, ~check) ? : CSUM_MANGLED_0;
+ /* On the TX path, CHECKSUM_NONE and CHECKSUM_UNNECESSARY have the same
+ * meaning. However, check for bad offloads in the GSO stack expects the
+ * latter, if the checksum was calculated in software. To vouch for the
+ * segment skbs we actually need to set it on the gso_skb.
+ */
+ if (gso_skb->ip_summed == CHECKSUM_NONE)
+ gso_skb->ip_summed = CHECKSUM_UNNECESSARY;
+
/* update refcount for the packet */
if (copy_dtor) {
int delta = sum_truesize - gso_skb->truesize;
--- a/net/ipv6/udp.c
+++ b/net/ipv6/udp.c
@@ -1258,8 +1258,7 @@ static int udp_v6_send_skb(struct sk_buf
kfree_skb(skb);
return -EINVAL;
}
- if (skb->ip_summed != CHECKSUM_PARTIAL || is_udplite ||
- dst_xfrm(skb_dst(skb))) {
+ if (is_udplite || dst_xfrm(skb_dst(skb))) {
kfree_skb(skb);
return -EIO;
}