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Diffstat (limited to 'src/xdp/common/parsing_helpers.h')
| -rw-r--r-- | src/xdp/common/parsing_helpers.h | 244 |
1 files changed, 244 insertions, 0 deletions
diff --git a/src/xdp/common/parsing_helpers.h b/src/xdp/common/parsing_helpers.h new file mode 100644 index 000000000..c0837e88f --- /dev/null +++ b/src/xdp/common/parsing_helpers.h @@ -0,0 +1,244 @@ +/* SPDX-License-Identifier: (GPL-2.0-or-later OR BSD-2-clause) */ +/* + * This file contains parsing functions that are used in the packetXX XDP + * programs. The functions are marked as __always_inline, and fully defined in + * this header file to be included in the BPF program. + * + * Each helper parses a packet header, including doing bounds checking, and + * returns the type of its contents if successful, and -1 otherwise. + * + * For Ethernet and IP headers, the content type is the type of the payload + * (h_proto for Ethernet, nexthdr for IPv6), for ICMP it is the ICMP type field. + * All return values are in host byte order. + * + * The versions of the functions included here are slightly expanded versions of + * the functions in the packet01 lesson. For instance, the Ethernet header + * parsing has support for parsing VLAN tags. + */ + +#ifndef __PARSING_HELPERS_H +#define __PARSING_HELPERS_H + +#include <stddef.h> +#include <linux/if_ether.h> +#include <linux/if_packet.h> +#include <linux/ip.h> +#include <linux/ipv6.h> +#include <linux/icmp.h> +#include <linux/icmpv6.h> +#include <linux/udp.h> +#include <linux/tcp.h> + +/* Header cursor to keep track of current parsing position */ +struct hdr_cursor { + void *pos; +}; + +/* + * struct vlan_hdr - vlan header + * @h_vlan_TCI: priority and VLAN ID + * @h_vlan_encapsulated_proto: packet type ID or len + */ +struct vlan_hdr { + __be16 h_vlan_TCI; + __be16 h_vlan_encapsulated_proto; +}; + +/* + * Struct icmphdr_common represents the common part of the icmphdr and icmp6hdr + * structures. + */ +struct icmphdr_common { + __u8 type; + __u8 code; + __sum16 cksum; +}; + +/* Allow users of header file to redefine VLAN max depth */ +#ifndef VLAN_MAX_DEPTH +#define VLAN_MAX_DEPTH 4 +#endif + +static __always_inline int proto_is_vlan(__u16 h_proto) +{ + return !!(h_proto == bpf_htons(ETH_P_8021Q) || + h_proto == bpf_htons(ETH_P_8021AD)); +} + +/* Notice, parse_ethhdr() will skip VLAN tags, by advancing nh->pos and returns + * next header EtherType, BUT the ethhdr pointer supplied still points to the + * Ethernet header. Thus, caller can look at eth->h_proto to see if this was a + * VLAN tagged packet. + */ +static __always_inline int parse_ethhdr(struct hdr_cursor *nh, void *data_end, + struct ethhdr **ethhdr) +{ + struct ethhdr *eth = nh->pos; + int hdrsize = sizeof(*eth); + struct vlan_hdr *vlh; + __u16 h_proto; + int i; + + /* Byte-count bounds check; check if current pointer + size of header + * is after data_end. + */ + if (nh->pos + hdrsize > data_end) + return -1; + + nh->pos += hdrsize; + *ethhdr = eth; + vlh = nh->pos; + h_proto = eth->h_proto; + + /* Use loop unrolling to avoid the verifier restriction on loops; + * support up to VLAN_MAX_DEPTH layers of VLAN encapsulation. + */ + #pragma unroll + for (i = 0; i < VLAN_MAX_DEPTH; i++) { + if (!proto_is_vlan(h_proto)) + break; + + if (vlh + 1 > data_end) + break; + + h_proto = vlh->h_vlan_encapsulated_proto; + vlh++; + } + + nh->pos = vlh; + return h_proto; /* network-byte-order */ +} + +static __always_inline int parse_ip6hdr(struct hdr_cursor *nh, + void *data_end, + struct ipv6hdr **ip6hdr) +{ + struct ipv6hdr *ip6h = nh->pos; + + /* Pointer-arithmetic bounds check; pointer +1 points to after end of + * thing being pointed to. We will be using this style in the remainder + * of the tutorial. + */ + if (ip6h + 1 > data_end) + return -1; + + nh->pos = ip6h + 1; + *ip6hdr = ip6h; + + return ip6h->nexthdr; +} + +static __always_inline int parse_iphdr(struct hdr_cursor *nh, + void *data_end, + struct iphdr **iphdr) +{ + struct iphdr *iph = nh->pos; + int hdrsize; + + if (iph + 1 > data_end) + return -1; + + hdrsize = iph->ihl * 4; + + /* Variable-length IPv4 header, need to use byte-based arithmetic */ + if (nh->pos + hdrsize > data_end) + return -1; + + nh->pos += hdrsize; + *iphdr = iph; + + return iph->protocol; +} + +static __always_inline int parse_icmp6hdr(struct hdr_cursor *nh, + void *data_end, + struct icmp6hdr **icmp6hdr) +{ + struct icmp6hdr *icmp6h = nh->pos; + + if (icmp6h + 1 > data_end) + return -1; + + nh->pos = icmp6h + 1; + *icmp6hdr = icmp6h; + + return icmp6h->icmp6_type; +} + +static __always_inline int parse_icmphdr(struct hdr_cursor *nh, + void *data_end, + struct icmphdr **icmphdr) +{ + struct icmphdr *icmph = nh->pos; + + if (icmph + 1 > data_end) + return -1; + + nh->pos = icmph + 1; + *icmphdr = icmph; + + return icmph->type; +} + +static __always_inline int parse_icmphdr_common(struct hdr_cursor *nh, + void *data_end, + struct icmphdr_common **icmphdr) +{ + struct icmphdr_common *h = nh->pos; + + if (h + 1 > data_end) + return -1; + + nh->pos = h + 1; + *icmphdr = h; + + return h->type; +} + +/* + * parse_udphdr: parse the udp header and return the length of the udp payload + */ +static __always_inline int parse_udphdr(struct hdr_cursor *nh, + void *data_end, + struct udphdr **udphdr) +{ + int len; + struct udphdr *h = nh->pos; + + if (h + 1 > data_end) + return -1; + + nh->pos = h + 1; + *udphdr = h; + + len = bpf_ntohs(h->len) - sizeof(struct udphdr); + if (len < 0) + return -1; + + return len; +} + +/* + * parse_tcphdr: parse and return the length of the tcp header + */ +static __always_inline int parse_tcphdr(struct hdr_cursor *nh, + void *data_end, + struct tcphdr **tcphdr) +{ + int len; + struct tcphdr *h = nh->pos; + + if (h + 1 > data_end) + return -1; + + len = h->doff * 4; + if ((void *) h + len > data_end) + return -1; + + nh->pos = h + 1; + *tcphdr = h; + + return len; +} + +#endif /* __PARSING_HELPERS_H */ |