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linux/include/net/inet_ecn.h
Toke Høiland-Jørgensen b723748750 tunnel: Propagate ECT(1) when decapsulating as recommended by RFC6040 
RFC 6040 recommends propagating an ECT(1) mark from an outer tunnel header
to the inner header if that inner header is already marked as ECT(0). When
RFC 6040 decapsulation was implemented, this case of propagation was not
added. This simply appears to be an oversight, so let's fix that.

Fixes: eccc1bb8d4 ("tunnel: drop packet if ECN present with not-ECT")
Reported-by: Bob Briscoe <ietf@bobbriscoe.net>
Reported-by: Olivier Tilmans <olivier.tilmans@nokia-bell-labs.com>
Cc: Dave Taht <dave.taht@gmail.com>
Cc: Stephen Hemminger <stephen@networkplumber.org>
Signed-off-by: Toke Høiland-Jørgensen <toke@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2020-04-30 20:32:15 -07:00

300 lines
7.4 KiB
C
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/* SPDX-License-Identifier: GPL-2.0 */
#ifndef _INET_ECN_H_
#define _INET_ECN_H_
#include <linux/ip.h>
#include <linux/skbuff.h>
#include <net/inet_sock.h>
#include <net/dsfield.h>
enum {
INET_ECN_NOT_ECT = 0,
INET_ECN_ECT_1 = 1,
INET_ECN_ECT_0 = 2,
INET_ECN_CE = 3,
INET_ECN_MASK = 3,
};
extern int sysctl_tunnel_ecn_log;
static inline int INET_ECN_is_ce(__u8 dsfield)
{
return (dsfield & INET_ECN_MASK) == INET_ECN_CE;
}
static inline int INET_ECN_is_not_ect(__u8 dsfield)
{
return (dsfield & INET_ECN_MASK) == INET_ECN_NOT_ECT;
}
static inline int INET_ECN_is_capable(__u8 dsfield)
{
return dsfield & INET_ECN_ECT_0;
}
/*
* RFC 3168 9.1.1
* The full-functionality option for ECN encapsulation is to copy the
* ECN codepoint of the inside header to the outside header on
* encapsulation if the inside header is not-ECT or ECT, and to set the
* ECN codepoint of the outside header to ECT(0) if the ECN codepoint of
* the inside header is CE.
*/
static inline __u8 INET_ECN_encapsulate(__u8 outer, __u8 inner)
{
outer &= ~INET_ECN_MASK;
outer |= !INET_ECN_is_ce(inner) ? (inner & INET_ECN_MASK) :
INET_ECN_ECT_0;
return outer;
}
static inline void INET_ECN_xmit(struct sock *sk)
{
inet_sk(sk)->tos |= INET_ECN_ECT_0;
if (inet6_sk(sk) != NULL)
inet6_sk(sk)->tclass |= INET_ECN_ECT_0;
}
static inline void INET_ECN_dontxmit(struct sock *sk)
{
inet_sk(sk)->tos &= ~INET_ECN_MASK;
if (inet6_sk(sk) != NULL)
inet6_sk(sk)->tclass &= ~INET_ECN_MASK;
}
#define IP6_ECN_flow_init(label) do { \
(label) &= ~htonl(INET_ECN_MASK << 20); \
} while (0)
#define IP6_ECN_flow_xmit(sk, label) do { \
if (INET_ECN_is_capable(inet6_sk(sk)->tclass)) \
(label) |= htonl(INET_ECN_ECT_0 << 20); \
} while (0)
static inline int IP_ECN_set_ce(struct iphdr *iph)
{
u32 check = (__force u32)iph->check;
u32 ecn = (iph->tos + 1) & INET_ECN_MASK;
/*
* After the last operation we have (in binary):
* INET_ECN_NOT_ECT => 01
* INET_ECN_ECT_1 => 10
* INET_ECN_ECT_0 => 11
* INET_ECN_CE => 00
*/
if (!(ecn & 2))
return !ecn;
/*
* The following gives us:
* INET_ECN_ECT_1 => check += htons(0xFFFD)
* INET_ECN_ECT_0 => check += htons(0xFFFE)
*/
check += (__force u16)htons(0xFFFB) + (__force u16)htons(ecn);
iph->check = (__force __sum16)(check + (check>=0xFFFF));
iph->tos |= INET_ECN_CE;
return 1;
}
static inline int IP_ECN_set_ect1(struct iphdr *iph)
{
u32 check = (__force u32)iph->check;
if ((iph->tos & INET_ECN_MASK) != INET_ECN_ECT_0)
return 0;
check += (__force u16)htons(0x100);
iph->check = (__force __sum16)(check + (check>=0xFFFF));
iph->tos ^= INET_ECN_MASK;
return 1;
}
static inline void IP_ECN_clear(struct iphdr *iph)
{
iph->tos &= ~INET_ECN_MASK;
}
static inline void ipv4_copy_dscp(unsigned int dscp, struct iphdr *inner)
{
dscp &= ~INET_ECN_MASK;
ipv4_change_dsfield(inner, INET_ECN_MASK, dscp);
}
struct ipv6hdr;
/* Note:
* IP_ECN_set_ce() has to tweak IPV4 checksum when setting CE,
* meaning both changes have no effect on skb->csum if/when CHECKSUM_COMPLETE
* In IPv6 case, no checksum compensates the change in IPv6 header,
* so we have to update skb->csum.
*/
static inline int IP6_ECN_set_ce(struct sk_buff *skb, struct ipv6hdr *iph)
{
__be32 from, to;
if (INET_ECN_is_not_ect(ipv6_get_dsfield(iph)))
return 0;
from = *(__be32 *)iph;
to = from | htonl(INET_ECN_CE << 20);
*(__be32 *)iph = to;
if (skb->ip_summed == CHECKSUM_COMPLETE)
skb->csum = csum_add(csum_sub(skb->csum, (__force __wsum)from),
(__force __wsum)to);
return 1;
}
static inline int IP6_ECN_set_ect1(struct sk_buff *skb, struct ipv6hdr *iph)
{
__be32 from, to;
if ((ipv6_get_dsfield(iph) & INET_ECN_MASK) != INET_ECN_ECT_0)
return 0;
from = *(__be32 *)iph;
to = from ^ htonl(INET_ECN_MASK << 20);
*(__be32 *)iph = to;
if (skb->ip_summed == CHECKSUM_COMPLETE)
skb->csum = csum_add(csum_sub(skb->csum, (__force __wsum)from),
(__force __wsum)to);
return 1;
}
static inline void ipv6_copy_dscp(unsigned int dscp, struct ipv6hdr *inner)
{
dscp &= ~INET_ECN_MASK;
ipv6_change_dsfield(inner, INET_ECN_MASK, dscp);
}
static inline int INET_ECN_set_ce(struct sk_buff *skb)
{
switch (skb->protocol) {
case cpu_to_be16(ETH_P_IP):
if (skb_network_header(skb) + sizeof(struct iphdr) <=
skb_tail_pointer(skb))
return IP_ECN_set_ce(ip_hdr(skb));
break;
case cpu_to_be16(ETH_P_IPV6):
if (skb_network_header(skb) + sizeof(struct ipv6hdr) <=
skb_tail_pointer(skb))
return IP6_ECN_set_ce(skb, ipv6_hdr(skb));
break;
}
return 0;
}
static inline int INET_ECN_set_ect1(struct sk_buff *skb)
{
switch (skb->protocol) {
case cpu_to_be16(ETH_P_IP):
if (skb_network_header(skb) + sizeof(struct iphdr) <=
skb_tail_pointer(skb))
return IP_ECN_set_ect1(ip_hdr(skb));
break;
case cpu_to_be16(ETH_P_IPV6):
if (skb_network_header(skb) + sizeof(struct ipv6hdr) <=
skb_tail_pointer(skb))
return IP6_ECN_set_ect1(skb, ipv6_hdr(skb));
break;
}
return 0;
}
/*
* RFC 6040 4.2
* To decapsulate the inner header at the tunnel egress, a compliant
* tunnel egress MUST set the outgoing ECN field to the codepoint at the
* intersection of the appropriate arriving inner header (row) and outer
* header (column) in Figure 4
*
* +---------+------------------------------------------------+
* |Arriving | Arriving Outer Header |
* | Inner +---------+------------+------------+------------+
* | Header | Not-ECT | ECT(0) | ECT(1) | CE |
* +---------+---------+------------+------------+------------+
* | Not-ECT | Not-ECT |Not-ECT(!!!)|Not-ECT(!!!)| <drop>(!!!)|
* | ECT(0) | ECT(0) | ECT(0) | ECT(1) | CE |
* | ECT(1) | ECT(1) | ECT(1) (!) | ECT(1) | CE |
* | CE | CE | CE | CE(!!!)| CE |
* +---------+---------+------------+------------+------------+
*
* Figure 4: New IP in IP Decapsulation Behaviour
*
* returns 0 on success
* 1 if something is broken and should be logged (!!! above)
* 2 if packet should be dropped
*/
static inline int __INET_ECN_decapsulate(__u8 outer, __u8 inner, bool *set_ce)
{
if (INET_ECN_is_not_ect(inner)) {
switch (outer & INET_ECN_MASK) {
case INET_ECN_NOT_ECT:
return 0;
case INET_ECN_ECT_0:
case INET_ECN_ECT_1:
return 1;
case INET_ECN_CE:
return 2;
}
}
*set_ce = INET_ECN_is_ce(outer);
return 0;
}
static inline int INET_ECN_decapsulate(struct sk_buff *skb,
__u8 outer, __u8 inner)
{
bool set_ce = false;
int rc;
rc = __INET_ECN_decapsulate(outer, inner, &set_ce);
if (!rc) {
if (set_ce)
INET_ECN_set_ce(skb);
else if ((outer & INET_ECN_MASK) == INET_ECN_ECT_1)
INET_ECN_set_ect1(skb);
}
return rc;
}
static inline int IP_ECN_decapsulate(const struct iphdr *oiph,
struct sk_buff *skb)
{
__u8 inner;
if (skb->protocol == htons(ETH_P_IP))
inner = ip_hdr(skb)->tos;
else if (skb->protocol == htons(ETH_P_IPV6))
inner = ipv6_get_dsfield(ipv6_hdr(skb));
else
return 0;
return INET_ECN_decapsulate(skb, oiph->tos, inner);
}
static inline int IP6_ECN_decapsulate(const struct ipv6hdr *oipv6h,
struct sk_buff *skb)
{
__u8 inner;
if (skb->protocol == htons(ETH_P_IP))
inner = ip_hdr(skb)->tos;
else if (skb->protocol == htons(ETH_P_IPV6))
inner = ipv6_get_dsfield(ipv6_hdr(skb));
else
return 0;
return INET_ECN_decapsulate(skb, ipv6_get_dsfield(oipv6h), inner);
}
#endif
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