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https://github.com/torvalds/linux
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a166151cbe
For the short-term solution, lets fix bpf helper functions to use skb->mac_header relative offsets instead of skb->data in order to get the same eBPF programs with cls_bpf and act_bpf work on ingress and egress qdisc path. We need to ensure that mac_header is set before calling into programs. This is effectively the first option from below referenced discussion. More long term solution for LD_ABS|LD_IND instructions will be more intrusive but also more beneficial than this, and implemented later as it's too risky at this point in time. I.e., we plan to look into the option of moving skb_pull() out of eth_type_trans() and into netif_receive_skb() as has been suggested as second option. Meanwhile, this solution ensures ingress can be used with eBPF, too, and that we won't run into ABI troubles later. For dealing with negative offsets inside eBPF helper functions, we've implemented bpf_skb_clone_unwritable() to test for unwriteable headers. Reference: http://thread.gmane.org/gmane.linux.network/359129/focus=359694 Fixes:608cd71a9c("tc: bpf: generalize pedit action") Fixes:91bc4822c3("tc: bpf: add checksum helpers") Signed-off-by: Alexei Starovoitov <ast@plumgrid.com> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Signed-off-by: David S. Miller <davem@davemloft.net>
67 lines
2 KiB
C
67 lines
2 KiB
C
#include <uapi/linux/bpf.h>
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#include <uapi/linux/if_ether.h>
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#include <uapi/linux/if_packet.h>
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#include <uapi/linux/ip.h>
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#include <uapi/linux/in.h>
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#include <uapi/linux/tcp.h>
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#include <uapi/linux/filter.h>
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#include "bpf_helpers.h"
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/* compiler workaround */
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#define _htonl __builtin_bswap32
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static inline void set_dst_mac(struct __sk_buff *skb, char *mac)
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{
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bpf_skb_store_bytes(skb, 0, mac, ETH_ALEN, 1);
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}
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#define IP_CSUM_OFF (ETH_HLEN + offsetof(struct iphdr, check))
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#define TOS_OFF (ETH_HLEN + offsetof(struct iphdr, tos))
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static inline void set_ip_tos(struct __sk_buff *skb, __u8 new_tos)
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{
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__u8 old_tos = load_byte(skb, BPF_LL_OFF + TOS_OFF);
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bpf_l3_csum_replace(skb, IP_CSUM_OFF, htons(old_tos), htons(new_tos), 2);
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bpf_skb_store_bytes(skb, TOS_OFF, &new_tos, sizeof(new_tos), 0);
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}
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#define TCP_CSUM_OFF (ETH_HLEN + sizeof(struct iphdr) + offsetof(struct tcphdr, check))
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#define IP_SRC_OFF (ETH_HLEN + offsetof(struct iphdr, saddr))
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#define IS_PSEUDO 0x10
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static inline void set_tcp_ip_src(struct __sk_buff *skb, __u32 new_ip)
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{
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__u32 old_ip = _htonl(load_word(skb, BPF_LL_OFF + IP_SRC_OFF));
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bpf_l4_csum_replace(skb, TCP_CSUM_OFF, old_ip, new_ip, IS_PSEUDO | sizeof(new_ip));
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bpf_l3_csum_replace(skb, IP_CSUM_OFF, old_ip, new_ip, sizeof(new_ip));
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bpf_skb_store_bytes(skb, IP_SRC_OFF, &new_ip, sizeof(new_ip), 0);
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}
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#define TCP_DPORT_OFF (ETH_HLEN + sizeof(struct iphdr) + offsetof(struct tcphdr, dest))
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static inline void set_tcp_dest_port(struct __sk_buff *skb, __u16 new_port)
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{
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__u16 old_port = htons(load_half(skb, BPF_LL_OFF + TCP_DPORT_OFF));
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bpf_l4_csum_replace(skb, TCP_CSUM_OFF, old_port, new_port, sizeof(new_port));
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bpf_skb_store_bytes(skb, TCP_DPORT_OFF, &new_port, sizeof(new_port), 0);
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}
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SEC("classifier")
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int bpf_prog1(struct __sk_buff *skb)
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{
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__u8 proto = load_byte(skb, BPF_LL_OFF + ETH_HLEN + offsetof(struct iphdr, protocol));
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long *value;
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if (proto == IPPROTO_TCP) {
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set_ip_tos(skb, 8);
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set_tcp_ip_src(skb, 0xA010101);
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set_tcp_dest_port(skb, 5001);
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}
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return 0;
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}
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char _license[] SEC("license") = "GPL";
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