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linux-stable/tools/testing/selftests/bpf/progs/bpf_flow.c
Santucci Pierpaolo 024cd2cbd1 selftest/bpf: Fix IPV6FR handling in flow dissector 
From second fragment on, IPV6FR program must stop the dissection of IPV6
fragmented packet. This is the same approach used for IPV4 fragmentation.
This fixes the flow keys calculation for the upper-layer protocols.
Note that according to RFC8200, the first fragment packet must include
the upper-layer header.

Signed-off-by: Santucci Pierpaolo <santucci@epigenesys.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Reviewed-by: Jakub Sitnicki <jakub@cloudflare.com>
Link: https://lore.kernel.org/bpf/X7JUzUj34ceE2wBm@santucci.pierpaolo
2020-11-16 16:23:29 +01:00

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// 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>
int _version SEC("version") = 1;
#define PROG(F) PROG_(F, _##F)
#define PROG_(NUM, NAME) SEC("flow_dissector/"#NUM) int bpf_func##NAME
/* 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;
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->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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