// SPDX-License-Identifier: GPL-2.0
#include <limits.h>
#include <stddef.h>
#include <stdbool.h>
#include <string.h>
#include <linux/pkt_cls.h>
#include <linux/bpf.h>
#include <linux/in.h>
#include <linux/if_ether.h>
#include <linux/icmp.h>
#include <linux/ip.h>
#include <linux/ipv6.h>
#include <linux/tcp.h>
#include <linux/udp.h>
#include <linux/if_packet.h>
#include <sys/socket.h>
#include <linux/if_tunnel.h>
#include <linux/mpls.h>
#include <bpf/bpf_helpers.h>
#include <bpf/bpf_endian.h>
#define PROG(F) PROG_(F, _##F)
#define PROG_(NUM, NAME) SEC("flow_dissector") int flow_dissector_##NUM
#define FLOW_CONTINUE_SADDR 0x7f00007f /* 127.0.0.127 */
/* These are the identifiers of the BPF programs that will be used in tail
* calls. Name is limited to 16 characters, with the terminating character and
* bpf_func_ above, we have only 6 to work with, anything after will be cropped.
*/
#define IP 0
#define IPV6 1
#define IPV6OP 2 /* Destination/Hop-by-Hop Options IPv6 Ext. Header */
#define IPV6FR 3 /* Fragmentation IPv6 Extension Header */
#define MPLS 4
#define VLAN 5
#define MAX_PROG 6
#define IP_MF 0x2000
#define IP_OFFSET 0x1FFF
#define IP6_MF 0x0001
#define IP6_OFFSET 0xFFF8
struct vlan_hdr {
__be16 h_vlan_TCI;
__be16 h_vlan_encapsulated_proto;
};
struct gre_hdr {
__be16 flags;
__be16 proto;
};
struct frag_hdr {
__u8 nexthdr;
__u8 reserved;
__be16 frag_off;
__be32 identification;
};
struct {
__uint(type, BPF_MAP_TYPE_PROG_ARRAY);
__uint(max_entries, MAX_PROG);
__uint(key_size, sizeof(__u32));
__uint(value_size, sizeof(__u32));
} jmp_table SEC(".maps");
struct {
__uint(type, BPF_MAP_TYPE_HASH);
__uint(max_entries, 1024);
__type(key, __u32);
__type(value, struct bpf_flow_keys);
} last_dissection SEC(".maps");
static __always_inline int export_flow_keys(struct bpf_flow_keys *keys,
int ret)
{
__u32 key = (__u32)(keys->sport) << 16 | keys->dport;
struct bpf_flow_keys val;
memcpy(&val, keys, sizeof(val));
bpf_map_update_elem(&last_dissection, &key, &val, BPF_ANY);
return ret;
}
#define IPV6_FLOWLABEL_MASK __bpf_constant_htonl(0x000FFFFF)
static inline __be32 ip6_flowlabel(const struct ipv6hdr *hdr)
{
return *(__be32 *)hdr & IPV6_FLOWLABEL_MASK;
}
static __always_inline void *bpf_flow_dissect_get_header(struct __sk_buff *skb,
__u16 hdr_size,
void *buffer)
{
void *data_end = (void *)(long)skb->data_end;
void *data = (void *)(long)skb->data;
__u16 thoff = skb->flow_keys->thoff;
__u8 *hdr;
/* Verifies this variable offset does not overflow */
if (thoff > (USHRT_MAX - hdr_size))
return NULL;
hdr = data + thoff;
if (hdr + hdr_size <= data_end)
return hdr;
if (bpf_skb_load_bytes(skb, thoff, buffer, hdr_size))
return NULL;
return buffer;
}
/* Dispatches on ETHERTYPE */
static __always_inline int parse_eth_proto(struct __sk_buff *skb, __be16 proto)
{
struct bpf_flow_keys *keys = skb->flow_keys;
switch (proto) {
case bpf_htons(ETH_P_IP):
bpf_tail_call_static(skb, &jmp_table, IP);
break;
case bpf_htons(ETH_P_IPV6):
bpf_tail_call_static(skb, &jmp_table, IPV6);
break;
case bpf_htons(ETH_P_MPLS_MC):
case bpf_htons(ETH_P_MPLS_UC):
bpf_tail_call_static(skb, &jmp_table, MPLS);
break;
case bpf_htons(ETH_P_8021Q):
case bpf_htons(ETH_P_8021AD):
bpf_tail_call_static(skb, &jmp_table, VLAN);
break;
default:
/* Protocol not supported */
return export_flow_keys(keys, BPF_DROP);
}
return export_flow_keys(keys, BPF_DROP);
}
SEC("flow_dissector")
int _dissect(struct __sk_buff *skb)
{
struct bpf_flow_keys *keys = skb->flow_keys;
if (keys->n_proto == bpf_htons(ETH_P_IP)) {
/* IP traffic from FLOW_CONTINUE_SADDR falls-back to
* standard dissector
*/
struct iphdr *iph, _iph;
iph = bpf_flow_dissect_get_header(skb, sizeof(*iph), &_iph);
if (iph && iph->ihl == 5 &&
iph->saddr == bpf_htonl(FLOW_CONTINUE_SADDR)) {
return BPF_FLOW_DISSECTOR_CONTINUE;
}
}
return parse_eth_proto(skb, keys->n_proto);
}
/* Parses on IPPROTO_* */
static __always_inline int parse_ip_proto(struct __sk_buff *skb, __u8 proto)
{
struct bpf_flow_keys *keys = skb->flow_keys;
void *data_end = (void *)(long)skb->data_end;
struct icmphdr *icmp, _icmp;
struct gre_hdr *gre, _gre;
struct ethhdr *eth, _eth;
struct tcphdr *tcp, _tcp;
struct udphdr *udp, _udp;
switch (proto) {
case IPPROTO_ICMP:
icmp = bpf_flow_dissect_get_header(skb, sizeof(*icmp), &_icmp);
if (!icmp)
return export_flow_keys(keys, BPF_DROP);
return export_flow_keys(keys, BPF_OK);
case IPPROTO_IPIP:
keys->is_encap = true;
if (keys->flags & BPF_FLOW_DISSECTOR_F_STOP_AT_ENCAP)
return export_flow_keys(keys, BPF_OK);
return parse_eth_proto(skb, bpf_htons(ETH_P_IP));
case IPPROTO_IPV6:
keys->is_encap = true;
if (keys->flags & BPF_FLOW_DISSECTOR_F_STOP_AT_ENCAP)
return export_flow_keys(keys, BPF_OK);
return parse_eth_proto(skb, bpf_htons(ETH_P_IPV6));
case IPPROTO_GRE:
gre = bpf_flow_dissect_get_header(skb, sizeof(*gre), &_gre);
if (!gre)
return export_flow_keys(keys, BPF_DROP);
if (bpf_htons(gre->flags & GRE_VERSION))
/* Only inspect standard GRE packets with version 0 */
return export_flow_keys(keys, BPF_OK);
keys->thoff += sizeof(*gre); /* Step over GRE Flags and Proto */
if (GRE_IS_CSUM(gre->flags))
keys->thoff += 4; /* Step over chksum and Padding */
if (GRE_IS_KEY(gre->flags))
keys->thoff += 4; /* Step over key */
if (GRE_IS_SEQ(gre->flags))
keys->thoff += 4; /* Step over sequence number */
keys->is_encap = true;
if (keys->flags & BPF_FLOW_DISSECTOR_F_STOP_AT_ENCAP)
return export_flow_keys(keys, BPF_OK);
if (gre->proto == bpf_htons(ETH_P_TEB)) {
eth = bpf_flow_dissect_get_header(skb, sizeof(*eth),
&_eth);
if (!eth)
return export_flow_keys(keys, BPF_DROP);
keys->thoff += sizeof(*eth);
return parse_eth_proto(skb, eth->h_proto);
} else {
return parse_eth_proto(skb, gre->proto);
}
case IPPROTO_TCP:
tcp = bpf_flow_dissect_get_header(skb, sizeof(*tcp), &_tcp);
if (!tcp)
return export_flow_keys(keys, BPF_DROP);
if (tcp->doff < 5)
return export_flow_keys(keys, BPF_DROP);
if ((__u8 *)tcp + (tcp->doff << 2) > data_end)
return export_flow_keys(keys, BPF_DROP);
keys->sport = tcp->source;
keys->dport = tcp->dest;
return export_flow_keys(keys, BPF_OK);
case IPPROTO_UDP:
case IPPROTO_UDPLITE:
udp = bpf_flow_dissect_get_header(skb, sizeof(*udp), &_udp);
if (!udp)
return export_flow_keys(keys, BPF_DROP);
keys->sport = udp->source;
keys->dport = udp->dest;
return export_flow_keys(keys, BPF_OK);
default:
return export_flow_keys(keys, BPF_DROP);
}
return export_flow_keys(keys, BPF_DROP);
}
static __always_inline int parse_ipv6_proto(struct __sk_buff *skb, __u8 nexthdr)
{
struct bpf_flow_keys *keys = skb->flow_keys;
switch (nexthdr) {
case IPPROTO_HOPOPTS:
case IPPROTO_DSTOPTS:
bpf_tail_call_static(skb, &jmp_table, IPV6OP);
break;
case IPPROTO_FRAGMENT:
bpf_tail_call_static(skb, &jmp_table, IPV6FR);
break;
default:
return parse_ip_proto(skb, nexthdr);
}
return export_flow_keys(keys, BPF_DROP);
}
PROG(IP)(struct __sk_buff *skb)
{
void *data_end = (void *)(long)skb->data_end;
struct bpf_flow_keys *keys = skb->flow_keys;
void *data = (void *)(long)skb->data;
struct iphdr *iph, _iph;
bool done = false;
iph = bpf_flow_dissect_get_header(skb, sizeof(*iph), &_iph);
if (!iph)
return export_flow_keys(keys, BPF_DROP);
/* IP header cannot be smaller than 20 bytes */
if (iph->ihl < 5)
return export_flow_keys(keys, BPF_DROP);
keys->addr_proto = ETH_P_IP;
keys->ipv4_src = iph->saddr;
keys->ipv4_dst = iph->daddr;
keys->ip_proto = iph->protocol;
keys->thoff += iph->ihl << 2;
if (data + keys->thoff > data_end)
return export_flow_keys(keys, BPF_DROP);
if (iph->frag_off & bpf_htons(IP_MF | IP_OFFSET)) {
keys->is_frag = true;
if (iph->frag_off & bpf_htons(IP_OFFSET)) {
/* From second fragment on, packets do not have headers
* we can parse.
*/
done = true;
} else {
keys->is_first_frag = true;
/* No need to parse fragmented packet unless
* explicitly asked for.
*/
if (!(keys->flags &
BPF_FLOW_DISSECTOR_F_PARSE_1ST_FRAG))
done = true;
}
}
if (done)
return export_flow_keys(keys, BPF_OK);
return parse_ip_proto(skb, iph->protocol);
}
PROG(IPV6)(struct __sk_buff *skb)
{
struct bpf_flow_keys *keys = skb->flow_keys;
struct ipv6hdr *ip6h, _ip6h;
ip6h = bpf_flow_dissect_get_header(skb, sizeof(*ip6h), &_ip6h);
if (!ip6h)
return export_flow_keys(keys, BPF_DROP);
keys->addr_proto = ETH_P_IPV6;
memcpy(&keys->ipv6_src, &ip6h->saddr, 2*sizeof(ip6h->saddr));
keys->thoff += sizeof(struct ipv6hdr);
keys->ip_proto = ip6h->nexthdr;
keys->flow_label = ip6_flowlabel(ip6h);
if (keys->flow_label && keys->flags & BPF_FLOW_DISSECTOR_F_STOP_AT_FLOW_LABEL)
return export_flow_keys(keys, BPF_OK);
return parse_ipv6_proto(skb, ip6h->nexthdr);
}
PROG(IPV6OP)(struct __sk_buff *skb)
{
struct bpf_flow_keys *keys = skb->flow_keys;
struct ipv6_opt_hdr *ip6h, _ip6h;
ip6h = bpf_flow_dissect_get_header(skb, sizeof(*ip6h), &_ip6h);
if (!ip6h)
return export_flow_keys(keys, BPF_DROP);
/* hlen is in 8-octets and does not include the first 8 bytes
* of the header
*/
keys->thoff += (1 + ip6h->hdrlen) << 3;
keys->ip_proto = ip6h->nexthdr;
return parse_ipv6_proto(skb, ip6h->nexthdr);
}
PROG(IPV6FR)(struct __sk_buff *skb)
{
struct bpf_flow_keys *keys = skb->flow_keys;
struct frag_hdr *fragh, _fragh;
fragh = bpf_flow_dissect_get_header(skb, sizeof(*fragh), &_fragh);
if (!fragh)
return export_flow_keys(keys, BPF_DROP);
keys->thoff += sizeof(*fragh);
keys->is_frag = true;
keys->ip_proto = fragh->nexthdr;
if (!(fragh->frag_off & bpf_htons(IP6_OFFSET))) {
keys->is_first_frag = true;
/* No need to parse fragmented packet unless
* explicitly asked for.
*/
if (!(keys->flags & BPF_FLOW_DISSECTOR_F_PARSE_1ST_FRAG))
return export_flow_keys(keys, BPF_OK);
} else {
return export_flow_keys(keys, BPF_OK);
}
return parse_ipv6_proto(skb, fragh->nexthdr);
}
PROG(MPLS)(struct __sk_buff *skb)
{
struct bpf_flow_keys *keys = skb->flow_keys;
struct mpls_label *mpls, _mpls;
mpls = bpf_flow_dissect_get_header(skb, sizeof(*mpls), &_mpls);
if (!mpls)
return export_flow_keys(keys, BPF_DROP);
return export_flow_keys(keys, BPF_OK);
}
PROG(VLAN)(struct __sk_buff *skb)
{
struct bpf_flow_keys *keys = skb->flow_keys;
struct vlan_hdr *vlan, _vlan;
/* Account for double-tagging */
if (keys->n_proto == bpf_htons(ETH_P_8021AD)) {
vlan = bpf_flow_dissect_get_header(skb, sizeof(*vlan), &_vlan);
if (!vlan)
return export_flow_keys(keys, BPF_DROP);
if (vlan->h_vlan_encapsulated_proto != bpf_htons(ETH_P_8021Q))
return export_flow_keys(keys, BPF_DROP);
keys->nhoff += sizeof(*vlan);
keys->thoff += sizeof(*vlan);
}
vlan = bpf_flow_dissect_get_header(skb, sizeof(*vlan), &_vlan);
if (!vlan)
return export_flow_keys(keys, BPF_DROP);
keys->nhoff += sizeof(*vlan);
keys->thoff += sizeof(*vlan);
/* Only allow 8021AD + 8021Q double tagging and no triple tagging.*/
if (vlan->h_vlan_encapsulated_proto == bpf_htons(ETH_P_8021AD) ||
vlan->h_vlan_encapsulated_proto == bpf_htons(ETH_P_8021Q))
return export_flow_keys(keys, BPF_DROP);
keys->n_proto = vlan->h_vlan_encapsulated_proto;
return parse_eth_proto(skb, vlan->h_vlan_encapsulated_proto);
}
char __license[] SEC("license") = "GPL";
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