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linux-loongson/include/linux/virtio_net.h
Paolo Abeni a2fb4bc4e2 net: implement virtio helpers to handle UDP GSO tunneling. 
The virtio specification are introducing support for GSO over UDP
tunnel.

This patch brings in the needed defines and the additional virtio hdr
parsing/building helpers.

The UDP tunnel support uses additional fields in the virtio hdr, and such
fields location can change depending on other negotiated features -
specifically VIRTIO_NET_F_HASH_REPORT.

Try to be as conservative as possible with the new field validation.

Existing implementation for plain GSO offloads allow for invalid/
self-contradictory values of such fields. With GSO over UDP tunnel we can
be more strict, with no need to deal with legacy implementation.

Since the checksum-related field validation is asymmetric in the driver
and in the device, introduce a separate helper to implement the new checks
(to be used only on the driver side).

Note that while the feature space exceeds the 64-bit boundaries, the
guest offload space is fixed by the specification of the
VIRTIO_NET_CTRL_GUEST_OFFLOADS_SET command to a 64-bit size.

Prior to the UDP tunnel GSO support, each guest offload bit corresponded
to the feature bit with the same value and vice versa.

Due to the limited 'guest offload' space, relevant features in the high
64 bits are 'mapped' to free bits in the lower range. That is simpler
than defining a new command (and associated features) to exchange an
extended guest offloads set.

As a consequence, the uAPIs also specify the mapped guest offload value
corresponding to the UDP tunnel GSO features.

Acked-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
--
v4 -> v5:
  - avoid lines above 80 chars

v3 -> v4:
  - fixed offset for UDP GSO tunnel, update accordingly the helpers
  - tried to clarified vlan_hlen semantic
  - virtio_net_chk_data_valid() -> virtio_net_handle_csum_offload()

v2 -> v3:
  - add definitions for possible vnet hdr layouts with tunnel support

v1 -> v2:
  - 'relay' -> 'rely' typo
  - less unclear comment WRT enforced inner GSO checks
  - inner header fields are allowed only with 'modern' virtio,
    thus are always le
  - clarified in the commit message the need for 'mapped features'
    defines
  - assume little_endian is true when UDP GSO is enabled.
  - fix inner proto type value
2025-07-08 18:05:47 +02:00

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/* SPDX-License-Identifier: GPL-2.0 */
#ifndef _LINUX_VIRTIO_NET_H
#define _LINUX_VIRTIO_NET_H
#include <linux/if_vlan.h>
#include <linux/ip.h>
#include <linux/ipv6.h>
#include <linux/udp.h>
#include <uapi/linux/tcp.h>
#include <uapi/linux/virtio_net.h>
static inline bool virtio_net_hdr_match_proto(__be16 protocol, __u8 gso_type)
{
switch (gso_type & ~VIRTIO_NET_HDR_GSO_ECN) {
case VIRTIO_NET_HDR_GSO_TCPV4:
return protocol == cpu_to_be16(ETH_P_IP);
case VIRTIO_NET_HDR_GSO_TCPV6:
return protocol == cpu_to_be16(ETH_P_IPV6);
case VIRTIO_NET_HDR_GSO_UDP:
case VIRTIO_NET_HDR_GSO_UDP_L4:
return protocol == cpu_to_be16(ETH_P_IP) ||
protocol == cpu_to_be16(ETH_P_IPV6);
default:
return false;
}
}
static inline int virtio_net_hdr_set_proto(struct sk_buff *skb,
const struct virtio_net_hdr *hdr)
{
if (skb->protocol)
return 0;
switch (hdr->gso_type & ~VIRTIO_NET_HDR_GSO_ECN) {
case VIRTIO_NET_HDR_GSO_TCPV4:
case VIRTIO_NET_HDR_GSO_UDP:
case VIRTIO_NET_HDR_GSO_UDP_L4:
skb->protocol = cpu_to_be16(ETH_P_IP);
break;
case VIRTIO_NET_HDR_GSO_TCPV6:
skb->protocol = cpu_to_be16(ETH_P_IPV6);
break;
default:
return -EINVAL;
}
return 0;
}
static inline int __virtio_net_hdr_to_skb(struct sk_buff *skb,
const struct virtio_net_hdr *hdr,
bool little_endian, u8 hdr_gso_type)
{
unsigned int nh_min_len = sizeof(struct iphdr);
unsigned int gso_type = 0;
unsigned int thlen = 0;
unsigned int p_off = 0;
unsigned int ip_proto;
if (hdr_gso_type != VIRTIO_NET_HDR_GSO_NONE) {
switch (hdr_gso_type & ~VIRTIO_NET_HDR_GSO_ECN) {
case VIRTIO_NET_HDR_GSO_TCPV4:
gso_type = SKB_GSO_TCPV4;
ip_proto = IPPROTO_TCP;
thlen = sizeof(struct tcphdr);
break;
case VIRTIO_NET_HDR_GSO_TCPV6:
gso_type = SKB_GSO_TCPV6;
ip_proto = IPPROTO_TCP;
thlen = sizeof(struct tcphdr);
nh_min_len = sizeof(struct ipv6hdr);
break;
case VIRTIO_NET_HDR_GSO_UDP:
gso_type = SKB_GSO_UDP;
ip_proto = IPPROTO_UDP;
thlen = sizeof(struct udphdr);
break;
case VIRTIO_NET_HDR_GSO_UDP_L4:
gso_type = SKB_GSO_UDP_L4;
ip_proto = IPPROTO_UDP;
thlen = sizeof(struct udphdr);
break;
default:
return -EINVAL;
}
if (hdr_gso_type & VIRTIO_NET_HDR_GSO_ECN)
gso_type |= SKB_GSO_TCP_ECN;
if (hdr->gso_size == 0)
return -EINVAL;
}
skb_reset_mac_header(skb);
if (hdr->flags & VIRTIO_NET_HDR_F_NEEDS_CSUM) {
u32 start = __virtio16_to_cpu(little_endian, hdr->csum_start);
u32 off = __virtio16_to_cpu(little_endian, hdr->csum_offset);
u32 needed = start + max_t(u32, thlen, off + sizeof(__sum16));
if (!pskb_may_pull(skb, needed))
return -EINVAL;
if (!skb_partial_csum_set(skb, start, off))
return -EINVAL;
if (skb_transport_offset(skb) < nh_min_len)
return -EINVAL;
nh_min_len = skb_transport_offset(skb);
p_off = nh_min_len + thlen;
if (!pskb_may_pull(skb, p_off))
return -EINVAL;
} else {
/* gso packets without NEEDS_CSUM do not set transport_offset.
* probe and drop if does not match one of the above types.
*/
if (gso_type && skb->network_header) {
struct flow_keys_basic keys;
if (!skb->protocol) {
__be16 protocol = dev_parse_header_protocol(skb);
if (!protocol)
virtio_net_hdr_set_proto(skb, hdr);
else if (!virtio_net_hdr_match_proto(protocol,
hdr_gso_type))
return -EINVAL;
else
skb->protocol = protocol;
}
retry:
if (!skb_flow_dissect_flow_keys_basic(NULL, skb, &keys,
NULL, 0, 0, 0,
0)) {
/* UFO does not specify ipv4 or 6: try both */
if (gso_type & SKB_GSO_UDP &&
skb->protocol == htons(ETH_P_IP)) {
skb->protocol = htons(ETH_P_IPV6);
goto retry;
}
return -EINVAL;
}
p_off = keys.control.thoff + thlen;
if (!pskb_may_pull(skb, p_off) ||
keys.basic.ip_proto != ip_proto)
return -EINVAL;
skb_set_transport_header(skb, keys.control.thoff);
} else if (gso_type) {
p_off = nh_min_len + thlen;
if (!pskb_may_pull(skb, p_off))
return -EINVAL;
}
}
if (hdr_gso_type != VIRTIO_NET_HDR_GSO_NONE) {
u16 gso_size = __virtio16_to_cpu(little_endian, hdr->gso_size);
unsigned int nh_off = p_off;
struct skb_shared_info *shinfo = skb_shinfo(skb);
switch (gso_type & ~SKB_GSO_TCP_ECN) {
case SKB_GSO_UDP:
/* UFO may not include transport header in gso_size. */
nh_off -= thlen;
break;
case SKB_GSO_UDP_L4:
if (!(hdr->flags & VIRTIO_NET_HDR_F_NEEDS_CSUM))
return -EINVAL;
if (skb->csum_offset != offsetof(struct udphdr, check))
return -EINVAL;
if (skb->len - p_off > gso_size * UDP_MAX_SEGMENTS)
return -EINVAL;
if (gso_type != SKB_GSO_UDP_L4)
return -EINVAL;
break;
case SKB_GSO_TCPV4:
case SKB_GSO_TCPV6:
if (skb->ip_summed == CHECKSUM_PARTIAL &&
skb->csum_offset != offsetof(struct tcphdr, check))
return -EINVAL;
break;
}
/* Kernel has a special handling for GSO_BY_FRAGS. */
if (gso_size == GSO_BY_FRAGS)
return -EINVAL;
/* Too small packets are not really GSO ones. */
if (skb->len - nh_off > gso_size) {
shinfo->gso_size = gso_size;
shinfo->gso_type = gso_type;
/* Header must be checked, and gso_segs computed. */
shinfo->gso_type |= SKB_GSO_DODGY;
shinfo->gso_segs = 0;
}
}
return 0;
}
static inline int virtio_net_hdr_to_skb(struct sk_buff *skb,
const struct virtio_net_hdr *hdr,
bool little_endian)
{
return __virtio_net_hdr_to_skb(skb, hdr, little_endian, hdr->gso_type);
}
static inline int virtio_net_hdr_from_skb(const struct sk_buff *skb,
struct virtio_net_hdr *hdr,
bool little_endian,
bool has_data_valid,
int vlan_hlen)
{
memset(hdr, 0, sizeof(*hdr)); /* no info leak */
if (skb_is_gso(skb)) {
struct skb_shared_info *sinfo = skb_shinfo(skb);
/* This is a hint as to how much should be linear. */
hdr->hdr_len = __cpu_to_virtio16(little_endian,
skb_headlen(skb));
hdr->gso_size = __cpu_to_virtio16(little_endian,
sinfo->gso_size);
if (sinfo->gso_type & SKB_GSO_TCPV4)
hdr->gso_type = VIRTIO_NET_HDR_GSO_TCPV4;
else if (sinfo->gso_type & SKB_GSO_TCPV6)
hdr->gso_type = VIRTIO_NET_HDR_GSO_TCPV6;
else if (sinfo->gso_type & SKB_GSO_UDP_L4)
hdr->gso_type = VIRTIO_NET_HDR_GSO_UDP_L4;
else
return -EINVAL;
if (sinfo->gso_type & SKB_GSO_TCP_ECN)
hdr->gso_type |= VIRTIO_NET_HDR_GSO_ECN;
} else
hdr->gso_type = VIRTIO_NET_HDR_GSO_NONE;
if (skb->ip_summed == CHECKSUM_PARTIAL) {
hdr->flags = VIRTIO_NET_HDR_F_NEEDS_CSUM;
hdr->csum_start = __cpu_to_virtio16(little_endian,
skb_checksum_start_offset(skb) + vlan_hlen);
hdr->csum_offset = __cpu_to_virtio16(little_endian,
skb->csum_offset);
} else if (has_data_valid &&
skb->ip_summed == CHECKSUM_UNNECESSARY) {
hdr->flags = VIRTIO_NET_HDR_F_DATA_VALID;
} /* else everything is zero */
return 0;
}
static inline unsigned int virtio_l3min(bool is_ipv6)
{
return is_ipv6 ? sizeof(struct ipv6hdr) : sizeof(struct iphdr);
}
static inline int
virtio_net_hdr_tnl_to_skb(struct sk_buff *skb,
const struct virtio_net_hdr_v1_hash_tunnel *vhdr,
bool tnl_hdr_negotiated,
bool tnl_csum_negotiated,
bool little_endian)
{
const struct virtio_net_hdr *hdr = (const struct virtio_net_hdr *)vhdr;
unsigned int inner_nh, outer_th, inner_th;
unsigned int inner_l3min, outer_l3min;
u8 gso_inner_type, gso_tunnel_type;
bool outer_isv6, inner_isv6;
int ret;
gso_tunnel_type = hdr->gso_type & VIRTIO_NET_HDR_GSO_UDP_TUNNEL;
if (!gso_tunnel_type)
return virtio_net_hdr_to_skb(skb, hdr, little_endian);
/* Tunnel not supported/negotiated, but the hdr asks for it. */
if (!tnl_hdr_negotiated)
return -EINVAL;
/* Either ipv4 or ipv6. */
if (gso_tunnel_type == VIRTIO_NET_HDR_GSO_UDP_TUNNEL)
return -EINVAL;
/* The UDP tunnel must carry a GSO packet, but no UFO. */
gso_inner_type = hdr->gso_type & ~(VIRTIO_NET_HDR_GSO_ECN |
VIRTIO_NET_HDR_GSO_UDP_TUNNEL);
if (!gso_inner_type || gso_inner_type == VIRTIO_NET_HDR_GSO_UDP)
return -EINVAL;
/* Rely on csum being present. */
if (!(hdr->flags & VIRTIO_NET_HDR_F_NEEDS_CSUM))
return -EINVAL;
/* Validate offsets. */
outer_isv6 = gso_tunnel_type & VIRTIO_NET_HDR_GSO_UDP_TUNNEL_IPV6;
inner_isv6 = gso_inner_type == VIRTIO_NET_HDR_GSO_TCPV6;
inner_l3min = virtio_l3min(inner_isv6);
outer_l3min = ETH_HLEN + virtio_l3min(outer_isv6);
inner_th = __virtio16_to_cpu(little_endian, hdr->csum_start);
inner_nh = le16_to_cpu(vhdr->inner_nh_offset);
outer_th = le16_to_cpu(vhdr->outer_th_offset);
if (outer_th < outer_l3min ||
inner_nh < outer_th + sizeof(struct udphdr) ||
inner_th < inner_nh + inner_l3min)
return -EINVAL;
/* Let the basic parsing deal with plain GSO features. */
ret = __virtio_net_hdr_to_skb(skb, hdr, true,
hdr->gso_type & ~gso_tunnel_type);
if (ret)
return ret;
/* In case of USO, the inner protocol is still unknown and
* `inner_isv6` is just a guess, additional parsing is needed.
* The previous validation ensures that accessing an ipv4 inner
* network header is safe.
*/
if (gso_inner_type == VIRTIO_NET_HDR_GSO_UDP_L4) {
struct iphdr *iphdr = (struct iphdr *)(skb->data + inner_nh);
inner_isv6 = iphdr->version == 6;
inner_l3min = virtio_l3min(inner_isv6);
if (inner_th < inner_nh + inner_l3min)
return -EINVAL;
}
skb_set_inner_protocol(skb, inner_isv6 ? htons(ETH_P_IPV6) :
htons(ETH_P_IP));
if (hdr->flags & VIRTIO_NET_HDR_F_UDP_TUNNEL_CSUM) {
if (!tnl_csum_negotiated)
return -EINVAL;
skb_shinfo(skb)->gso_type |= SKB_GSO_UDP_TUNNEL_CSUM;
} else {
skb_shinfo(skb)->gso_type |= SKB_GSO_UDP_TUNNEL;
}
skb->inner_transport_header = inner_th + skb_headroom(skb);
skb->inner_network_header = inner_nh + skb_headroom(skb);
skb->inner_mac_header = inner_nh + skb_headroom(skb);
skb->transport_header = outer_th + skb_headroom(skb);
skb->encapsulation = 1;
return 0;
}
/* Checksum-related fields validation for the driver */
static inline int virtio_net_handle_csum_offload(struct sk_buff *skb,
struct virtio_net_hdr *hdr,
bool tnl_csum_negotiated)
{
if (!(hdr->gso_type & VIRTIO_NET_HDR_GSO_UDP_TUNNEL)) {
if (!(hdr->flags & VIRTIO_NET_HDR_F_DATA_VALID))
return 0;
skb->ip_summed = CHECKSUM_UNNECESSARY;
if (!(hdr->flags & VIRTIO_NET_HDR_F_UDP_TUNNEL_CSUM))
return 0;
/* tunnel csum packets are invalid when the related
* feature has not been negotiated
*/
if (!tnl_csum_negotiated)
return -EINVAL;
skb->csum_level = 1;
return 0;
}
/* DATA_VALID is mutually exclusive with NEEDS_CSUM, and GSO
* over UDP tunnel requires the latter
*/
if (hdr->flags & VIRTIO_NET_HDR_F_DATA_VALID)
return -EINVAL;
return 0;
}
/*
* vlan_hlen always refers to the outermost MAC header. That also
* means it refers to the only MAC header, if the packet does not carry
* any encapsulation.
*/
static inline int
virtio_net_hdr_tnl_from_skb(const struct sk_buff *skb,
struct virtio_net_hdr_v1_hash_tunnel *vhdr,
bool tnl_hdr_negotiated,
bool little_endian,
int vlan_hlen)
{
struct virtio_net_hdr *hdr = (struct virtio_net_hdr *)vhdr;
unsigned int inner_nh, outer_th;
int tnl_gso_type;
int ret;
tnl_gso_type = skb_shinfo(skb)->gso_type & (SKB_GSO_UDP_TUNNEL |
SKB_GSO_UDP_TUNNEL_CSUM);
if (!tnl_gso_type)
return virtio_net_hdr_from_skb(skb, hdr, little_endian, false,
vlan_hlen);
/* Tunnel support not negotiated but skb ask for it. */
if (!tnl_hdr_negotiated)
return -EINVAL;
/* Let the basic parsing deal with plain GSO features. */
skb_shinfo(skb)->gso_type &= ~tnl_gso_type;
ret = virtio_net_hdr_from_skb(skb, hdr, true, false, vlan_hlen);
skb_shinfo(skb)->gso_type |= tnl_gso_type;
if (ret)
return ret;
if (skb->protocol == htons(ETH_P_IPV6))
hdr->gso_type |= VIRTIO_NET_HDR_GSO_UDP_TUNNEL_IPV6;
else
hdr->gso_type |= VIRTIO_NET_HDR_GSO_UDP_TUNNEL_IPV4;
if (skb_shinfo(skb)->gso_type & SKB_GSO_UDP_TUNNEL_CSUM)
hdr->flags |= VIRTIO_NET_HDR_F_UDP_TUNNEL_CSUM;
inner_nh = skb->inner_network_header - skb_headroom(skb);
outer_th = skb->transport_header - skb_headroom(skb);
vhdr->inner_nh_offset = cpu_to_le16(inner_nh);
vhdr->outer_th_offset = cpu_to_le16(outer_th);
return 0;
}
#endif /* _LINUX_VIRTIO_NET_H */
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