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Diffstat (limited to 'src/xdp/common/rewrite_helpers.h')
| -rw-r--r-- | src/xdp/common/rewrite_helpers.h | 144 |
1 files changed, 144 insertions, 0 deletions
diff --git a/src/xdp/common/rewrite_helpers.h b/src/xdp/common/rewrite_helpers.h new file mode 100644 index 000000000..a5d3e671d --- /dev/null +++ b/src/xdp/common/rewrite_helpers.h @@ -0,0 +1,144 @@ +/* SPDX-License-Identifier: (GPL-2.0-or-later OR BSD-2-clause) */ +/* + * This file contains functions that are used in the packetXX XDP programs to + * manipulate on packets data. The functions are marked as __always_inline, and + * fully defined in this header file to be included in the BPF program. + */ + +#ifndef __REWRITE_HELPERS_H +#define __REWRITE_HELPERS_H + +#include <linux/bpf.h> +#include <linux/ip.h> +#include <linux/ipv6.h> +#include <linux/if_ether.h> + +#include <bpf/bpf_helpers.h> +#include <bpf/bpf_endian.h> + +/* Pops the outermost VLAN tag off the packet. Returns the popped VLAN ID on + * success or negative errno on failure. + */ +static __always_inline int vlan_tag_pop(struct xdp_md *ctx, struct ethhdr *eth) +{ + void *data_end = (void *)(long)ctx->data_end; + struct ethhdr eth_cpy; + struct vlan_hdr *vlh; + __be16 h_proto; + int vlid; + + if (!proto_is_vlan(eth->h_proto)) + return -1; + + /* Careful with the parenthesis here */ + vlh = (void *)(eth + 1); + + /* Still need to do bounds checking */ + if (vlh + 1 > data_end) + return -1; + + /* Save vlan ID for returning, h_proto for updating Ethernet header */ + vlid = bpf_ntohs(vlh->h_vlan_TCI); + h_proto = vlh->h_vlan_encapsulated_proto; + + /* Make a copy of the outer Ethernet header before we cut it off */ + __builtin_memcpy(ð_cpy, eth, sizeof(eth_cpy)); + + /* Actually adjust the head pointer */ + if (bpf_xdp_adjust_head(ctx, (int)sizeof(*vlh))) + return -1; + + /* Need to re-evaluate data *and* data_end and do new bounds checking + * after adjusting head + */ + eth = (void *)(long)ctx->data; + data_end = (void *)(long)ctx->data_end; + if (eth + 1 > data_end) + return -1; + + /* Copy back the old Ethernet header and update the proto type */ + __builtin_memcpy(eth, ð_cpy, sizeof(*eth)); + eth->h_proto = h_proto; + + return vlid; +} + +/* Pushes a new VLAN tag after the Ethernet header. Returns 0 on success, + * -1 on failure. + */ +static __always_inline int vlan_tag_push(struct xdp_md *ctx, + struct ethhdr *eth, int vlid) +{ + void *data_end = (void *)(long)ctx->data_end; + struct ethhdr eth_cpy; + struct vlan_hdr *vlh; + + /* First copy the original Ethernet header */ + __builtin_memcpy(ð_cpy, eth, sizeof(eth_cpy)); + + /* Then add space in front of the packet */ + if (bpf_xdp_adjust_head(ctx, 0 - (int)sizeof(*vlh))) + return -1; + + /* Need to re-evaluate data_end and data after head adjustment, and + * bounds check, even though we know there is enough space (as we + * increased it). + */ + data_end = (void *)(long)ctx->data_end; + eth = (void *)(long)ctx->data; + + if (eth + 1 > data_end) + return -1; + + /* Copy back Ethernet header in the right place, populate VLAN tag with + * ID and proto, and set outer Ethernet header to VLAN type. + */ + __builtin_memcpy(eth, ð_cpy, sizeof(*eth)); + + vlh = (void *)(eth + 1); + + if (vlh + 1 > data_end) + return -1; + + vlh->h_vlan_TCI = bpf_htons(vlid); + vlh->h_vlan_encapsulated_proto = eth->h_proto; + + eth->h_proto = bpf_htons(ETH_P_8021Q); + return 0; +} + +/* + * Swaps destination and source MAC addresses inside an Ethernet header + */ +static __always_inline void swap_src_dst_mac(struct ethhdr *eth) +{ + __u8 h_tmp[ETH_ALEN]; + + __builtin_memcpy(h_tmp, eth->h_source, ETH_ALEN); + __builtin_memcpy(eth->h_source, eth->h_dest, ETH_ALEN); + __builtin_memcpy(eth->h_dest, h_tmp, ETH_ALEN); +} + +/* + * Swaps destination and source IPv6 addresses inside an IPv6 header + */ +static __always_inline void swap_src_dst_ipv6(struct ipv6hdr *ipv6) +{ + struct in6_addr tmp = ipv6->saddr; + + ipv6->saddr = ipv6->daddr; + ipv6->daddr = tmp; +} + +/* + * Swaps destination and source IPv4 addresses inside an IPv4 header + */ +static __always_inline void swap_src_dst_ipv4(struct iphdr *iphdr) +{ + __be32 tmp = iphdr->saddr; + + iphdr->saddr = iphdr->daddr; + iphdr->daddr = tmp; +} + +#endif /* __REWRITE_HELPERS_H */ |