910 lines
35 KiB
C
910 lines
35 KiB
C
/* SPDX-License-Identifier: LGPL-2.1+ */
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#include <arpa/inet.h>
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#include <assert.h>
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#include <errno.h>
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#include <fcntl.h>
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#include <linux/bpf_insn.h>
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#include <net/ethernet.h>
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#include <net/if.h>
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#include <netinet/ip.h>
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#include <netinet/ip6.h>
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#include <stddef.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <unistd.h>
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#include "alloc-util.h"
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#include "bpf-firewall.h"
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#include "bpf-program.h"
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#include "fd-util.h"
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#include "ip-address-access.h"
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#include "memory-util.h"
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#include "missing_syscall.h"
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#include "unit.h"
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#include "strv.h"
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#include "virt.h"
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enum {
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MAP_KEY_PACKETS,
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MAP_KEY_BYTES,
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};
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enum {
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ACCESS_ALLOWED = 1,
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ACCESS_DENIED = 2,
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};
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/* Compile instructions for one list of addresses, one direction and one specific verdict on matches. */
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static int add_lookup_instructions(
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BPFProgram *p,
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int map_fd,
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int protocol,
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bool is_ingress,
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int verdict) {
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int r, addr_offset, addr_size;
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assert(p);
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assert(map_fd >= 0);
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switch (protocol) {
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case ETH_P_IP:
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addr_size = sizeof(uint32_t);
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addr_offset = is_ingress ?
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offsetof(struct iphdr, saddr) :
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offsetof(struct iphdr, daddr);
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break;
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case ETH_P_IPV6:
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addr_size = 4 * sizeof(uint32_t);
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addr_offset = is_ingress ?
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offsetof(struct ip6_hdr, ip6_src.s6_addr) :
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offsetof(struct ip6_hdr, ip6_dst.s6_addr);
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break;
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default:
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return -EAFNOSUPPORT;
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}
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do {
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/* Compare IPv4 with one word instruction (32bit) */
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struct bpf_insn insn[] = {
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/* If skb->protocol != ETH_P_IP, skip this whole block. The offset will be set later. */
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BPF_JMP_IMM(BPF_JNE, BPF_REG_7, htobe16(protocol), 0),
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/*
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* Call into BPF_FUNC_skb_load_bytes to load the dst/src IP address
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*
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* R1: Pointer to the skb
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* R2: Data offset
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* R3: Destination buffer on the stack (r10 - 4)
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* R4: Number of bytes to read (4)
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*/
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BPF_MOV64_REG(BPF_REG_1, BPF_REG_6),
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BPF_MOV32_IMM(BPF_REG_2, addr_offset),
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BPF_MOV64_REG(BPF_REG_3, BPF_REG_10),
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BPF_ALU64_IMM(BPF_ADD, BPF_REG_3, -addr_size),
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BPF_MOV32_IMM(BPF_REG_4, addr_size),
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BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0, BPF_FUNC_skb_load_bytes),
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/*
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* Call into BPF_FUNC_map_lookup_elem to see if the address matches any entry in the
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* LPM trie map. For this to work, the prefixlen field of 'struct bpf_lpm_trie_key'
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* has to be set to the maximum possible value.
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*
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* On success, the looked up value is stored in R0. For this application, the actual
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* value doesn't matter, however; we just set the bit in @verdict in R8 if we found any
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* matching value.
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*/
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BPF_LD_MAP_FD(BPF_REG_1, map_fd),
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BPF_MOV64_REG(BPF_REG_2, BPF_REG_10),
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BPF_ALU64_IMM(BPF_ADD, BPF_REG_2, -addr_size - sizeof(uint32_t)),
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BPF_ST_MEM(BPF_W, BPF_REG_2, 0, addr_size * 8),
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BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0, BPF_FUNC_map_lookup_elem),
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BPF_JMP_IMM(BPF_JEQ, BPF_REG_0, 0, 1),
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BPF_ALU32_IMM(BPF_OR, BPF_REG_8, verdict),
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};
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/* Jump label fixup */
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insn[0].off = ELEMENTSOF(insn) - 1;
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r = bpf_program_add_instructions(p, insn, ELEMENTSOF(insn));
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if (r < 0)
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return r;
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} while (false);
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return 0;
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}
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static int add_instructions_for_ip_any(
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BPFProgram *p,
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int verdict) {
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int r;
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assert(p);
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const struct bpf_insn insn[] = {
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BPF_ALU32_IMM(BPF_OR, BPF_REG_8, verdict),
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};
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r = bpf_program_add_instructions(p, insn, 1);
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if (r < 0)
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return r;
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return 0;
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}
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static int bpf_firewall_compile_bpf(
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Unit *u,
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bool is_ingress,
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BPFProgram **ret,
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bool ip_allow_any,
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bool ip_deny_any) {
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const struct bpf_insn pre_insn[] = {
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/*
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* When the eBPF program is entered, R1 contains the address of the skb.
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* However, R1-R5 are scratch registers that are not preserved when calling
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* into kernel functions, so we need to save anything that's supposed to
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* stay around to R6-R9. Save the skb to R6.
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*/
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BPF_MOV64_REG(BPF_REG_6, BPF_REG_1),
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/*
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* Although we cannot access the skb data directly from eBPF programs used in this
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* scenario, the kernel has prepared some fields for us to access through struct __sk_buff.
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* Load the protocol (IPv4, IPv6) used by the packet in flight once and cache it in R7
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* for later use.
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*/
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BPF_LDX_MEM(BPF_W, BPF_REG_7, BPF_REG_6, offsetof(struct __sk_buff, protocol)),
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/*
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* R8 is used to keep track of whether any address check has explicitly allowed or denied the packet
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* through ACCESS_DENIED or ACCESS_ALLOWED bits. Reset them both to 0 in the beginning.
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*/
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BPF_MOV32_IMM(BPF_REG_8, 0),
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};
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/*
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* The access checkers compiled for the configured allowance and denial lists
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* write to R8 at runtime. The following code prepares for an early exit that
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* skip the accounting if the packet is denied.
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*
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* R0 = 1
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* if (R8 == ACCESS_DENIED)
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* R0 = 0
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*
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* This means that if both ACCESS_DENIED and ACCESS_ALLOWED are set, the packet
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* is allowed to pass.
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*/
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const struct bpf_insn post_insn[] = {
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BPF_MOV64_IMM(BPF_REG_0, 1),
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BPF_JMP_IMM(BPF_JNE, BPF_REG_8, ACCESS_DENIED, 1),
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BPF_MOV64_IMM(BPF_REG_0, 0),
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};
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_cleanup_(bpf_program_unrefp) BPFProgram *p = NULL;
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int accounting_map_fd, r;
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bool access_enabled;
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assert(u);
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assert(ret);
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accounting_map_fd = is_ingress ?
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u->ip_accounting_ingress_map_fd :
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u->ip_accounting_egress_map_fd;
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access_enabled =
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u->ipv4_allow_map_fd >= 0 ||
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u->ipv6_allow_map_fd >= 0 ||
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u->ipv4_deny_map_fd >= 0 ||
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u->ipv6_deny_map_fd >= 0 ||
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ip_allow_any ||
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ip_deny_any;
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if (accounting_map_fd < 0 && !access_enabled) {
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*ret = NULL;
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return 0;
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}
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r = bpf_program_new(BPF_PROG_TYPE_CGROUP_SKB, &p);
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if (r < 0)
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return r;
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r = bpf_program_add_instructions(p, pre_insn, ELEMENTSOF(pre_insn));
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if (r < 0)
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return r;
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if (access_enabled) {
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/*
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* The simple rule this function translates into eBPF instructions is:
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*
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* - Access will be granted when an address matches an entry in @list_allow
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* - Otherwise, access will be denied when an address matches an entry in @list_deny
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* - Otherwise, access will be granted
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*/
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if (u->ipv4_deny_map_fd >= 0) {
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r = add_lookup_instructions(p, u->ipv4_deny_map_fd, ETH_P_IP, is_ingress, ACCESS_DENIED);
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if (r < 0)
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return r;
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}
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if (u->ipv6_deny_map_fd >= 0) {
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r = add_lookup_instructions(p, u->ipv6_deny_map_fd, ETH_P_IPV6, is_ingress, ACCESS_DENIED);
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if (r < 0)
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return r;
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}
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if (u->ipv4_allow_map_fd >= 0) {
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r = add_lookup_instructions(p, u->ipv4_allow_map_fd, ETH_P_IP, is_ingress, ACCESS_ALLOWED);
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if (r < 0)
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return r;
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}
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if (u->ipv6_allow_map_fd >= 0) {
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r = add_lookup_instructions(p, u->ipv6_allow_map_fd, ETH_P_IPV6, is_ingress, ACCESS_ALLOWED);
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if (r < 0)
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return r;
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}
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if (ip_allow_any) {
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r = add_instructions_for_ip_any(p, ACCESS_ALLOWED);
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if (r < 0)
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return r;
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}
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if (ip_deny_any) {
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r = add_instructions_for_ip_any(p, ACCESS_DENIED);
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if (r < 0)
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return r;
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}
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}
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r = bpf_program_add_instructions(p, post_insn, ELEMENTSOF(post_insn));
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if (r < 0)
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return r;
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if (accounting_map_fd >= 0) {
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struct bpf_insn insn[] = {
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/*
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* If R0 == 0, the packet will be denied; skip the accounting instructions in this case.
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* The jump label will be fixed up later.
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*/
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BPF_JMP_IMM(BPF_JEQ, BPF_REG_0, 0, 0),
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/* Count packets */
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BPF_MOV64_IMM(BPF_REG_0, MAP_KEY_PACKETS), /* r0 = 0 */
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BPF_STX_MEM(BPF_W, BPF_REG_10, BPF_REG_0, -4), /* *(u32 *)(fp - 4) = r0 */
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BPF_MOV64_REG(BPF_REG_2, BPF_REG_10),
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BPF_ALU64_IMM(BPF_ADD, BPF_REG_2, -4), /* r2 = fp - 4 */
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BPF_LD_MAP_FD(BPF_REG_1, accounting_map_fd), /* load map fd to r1 */
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BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0, BPF_FUNC_map_lookup_elem),
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BPF_JMP_IMM(BPF_JEQ, BPF_REG_0, 0, 2),
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BPF_MOV64_IMM(BPF_REG_1, 1), /* r1 = 1 */
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BPF_RAW_INSN(BPF_STX | BPF_XADD | BPF_DW, BPF_REG_0, BPF_REG_1, 0, 0), /* xadd r0 += r1 */
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/* Count bytes */
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BPF_MOV64_IMM(BPF_REG_0, MAP_KEY_BYTES), /* r0 = 1 */
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BPF_STX_MEM(BPF_W, BPF_REG_10, BPF_REG_0, -4), /* *(u32 *)(fp - 4) = r0 */
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BPF_MOV64_REG(BPF_REG_2, BPF_REG_10),
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BPF_ALU64_IMM(BPF_ADD, BPF_REG_2, -4), /* r2 = fp - 4 */
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BPF_LD_MAP_FD(BPF_REG_1, accounting_map_fd),
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BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0, BPF_FUNC_map_lookup_elem),
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BPF_JMP_IMM(BPF_JEQ, BPF_REG_0, 0, 2),
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BPF_LDX_MEM(BPF_W, BPF_REG_1, BPF_REG_6, offsetof(struct __sk_buff, len)), /* r1 = skb->len */
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BPF_RAW_INSN(BPF_STX | BPF_XADD | BPF_DW, BPF_REG_0, BPF_REG_1, 0, 0), /* xadd r0 += r1 */
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/* Allow the packet to pass */
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BPF_MOV64_IMM(BPF_REG_0, 1),
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};
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/* Jump label fixup */
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insn[0].off = ELEMENTSOF(insn) - 1;
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r = bpf_program_add_instructions(p, insn, ELEMENTSOF(insn));
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if (r < 0)
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return r;
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}
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do {
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/*
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* Exit from the eBPF program, R0 contains the verdict.
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* 0 means the packet is denied, 1 means the packet may pass.
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*/
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const struct bpf_insn insn[] = {
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BPF_EXIT_INSN()
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};
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r = bpf_program_add_instructions(p, insn, ELEMENTSOF(insn));
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if (r < 0)
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return r;
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} while (false);
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*ret = TAKE_PTR(p);
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return 0;
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}
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static int bpf_firewall_count_access_items(IPAddressAccessItem *list, size_t *n_ipv4, size_t *n_ipv6) {
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IPAddressAccessItem *a;
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assert(n_ipv4);
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assert(n_ipv6);
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LIST_FOREACH(items, a, list) {
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switch (a->family) {
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case AF_INET:
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(*n_ipv4)++;
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break;
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case AF_INET6:
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(*n_ipv6)++;
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break;
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default:
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return -EAFNOSUPPORT;
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}
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}
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return 0;
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}
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static int bpf_firewall_add_access_items(
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IPAddressAccessItem *list,
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int ipv4_map_fd,
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int ipv6_map_fd,
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int verdict) {
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struct bpf_lpm_trie_key *key_ipv4, *key_ipv6;
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uint64_t value = verdict;
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IPAddressAccessItem *a;
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int r;
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key_ipv4 = alloca0(offsetof(struct bpf_lpm_trie_key, data) + sizeof(uint32_t));
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key_ipv6 = alloca0(offsetof(struct bpf_lpm_trie_key, data) + sizeof(uint32_t) * 4);
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LIST_FOREACH(items, a, list) {
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switch (a->family) {
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case AF_INET:
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key_ipv4->prefixlen = a->prefixlen;
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memcpy(key_ipv4->data, &a->address, sizeof(uint32_t));
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r = bpf_map_update_element(ipv4_map_fd, key_ipv4, &value);
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if (r < 0)
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return r;
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break;
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case AF_INET6:
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key_ipv6->prefixlen = a->prefixlen;
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memcpy(key_ipv6->data, &a->address, 4 * sizeof(uint32_t));
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r = bpf_map_update_element(ipv6_map_fd, key_ipv6, &value);
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if (r < 0)
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return r;
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break;
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default:
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return -EAFNOSUPPORT;
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}
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}
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return 0;
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}
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static int bpf_firewall_prepare_access_maps(
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Unit *u,
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int verdict,
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int *ret_ipv4_map_fd,
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int *ret_ipv6_map_fd,
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bool *ret_has_any) {
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_cleanup_close_ int ipv4_map_fd = -1, ipv6_map_fd = -1;
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size_t n_ipv4 = 0, n_ipv6 = 0;
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IPAddressAccessItem *list;
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Unit *p;
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int r;
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assert(ret_ipv4_map_fd);
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assert(ret_ipv6_map_fd);
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assert(ret_has_any);
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for (p = u; p; p = UNIT_DEREF(p->slice)) {
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CGroupContext *cc;
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cc = unit_get_cgroup_context(p);
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if (!cc)
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continue;
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list = verdict == ACCESS_ALLOWED ? cc->ip_address_allow : cc->ip_address_deny;
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bpf_firewall_count_access_items(list, &n_ipv4, &n_ipv6);
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/* Skip making the LPM trie map in cases where we are using "any" in order to hack around
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* needing CAP_SYS_ADMIN for allocating LPM trie map. */
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if (ip_address_access_item_is_any(list)) {
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*ret_has_any = true;
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return 0;
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}
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}
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if (n_ipv4 > 0) {
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ipv4_map_fd = bpf_map_new(
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BPF_MAP_TYPE_LPM_TRIE,
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offsetof(struct bpf_lpm_trie_key, data) + sizeof(uint32_t),
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sizeof(uint64_t),
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n_ipv4,
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BPF_F_NO_PREALLOC);
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if (ipv4_map_fd < 0)
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return ipv4_map_fd;
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}
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if (n_ipv6 > 0) {
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ipv6_map_fd = bpf_map_new(
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BPF_MAP_TYPE_LPM_TRIE,
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offsetof(struct bpf_lpm_trie_key, data) + sizeof(uint32_t)*4,
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sizeof(uint64_t),
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n_ipv6,
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BPF_F_NO_PREALLOC);
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if (ipv6_map_fd < 0)
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return ipv6_map_fd;
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}
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for (p = u; p; p = UNIT_DEREF(p->slice)) {
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CGroupContext *cc;
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cc = unit_get_cgroup_context(p);
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if (!cc)
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continue;
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r = bpf_firewall_add_access_items(verdict == ACCESS_ALLOWED ? cc->ip_address_allow : cc->ip_address_deny,
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ipv4_map_fd, ipv6_map_fd, verdict);
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if (r < 0)
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return r;
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}
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*ret_ipv4_map_fd = TAKE_FD(ipv4_map_fd);
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*ret_ipv6_map_fd = TAKE_FD(ipv6_map_fd);
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*ret_has_any = false;
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return 0;
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}
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static int bpf_firewall_prepare_accounting_maps(Unit *u, bool enabled, int *fd_ingress, int *fd_egress) {
|
|
int r;
|
|
|
|
assert(u);
|
|
assert(fd_ingress);
|
|
assert(fd_egress);
|
|
|
|
if (enabled) {
|
|
if (*fd_ingress < 0) {
|
|
r = bpf_map_new(BPF_MAP_TYPE_ARRAY, sizeof(int), sizeof(uint64_t), 2, 0);
|
|
if (r < 0)
|
|
return r;
|
|
|
|
*fd_ingress = r;
|
|
}
|
|
|
|
if (*fd_egress < 0) {
|
|
|
|
r = bpf_map_new(BPF_MAP_TYPE_ARRAY, sizeof(int), sizeof(uint64_t), 2, 0);
|
|
if (r < 0)
|
|
return r;
|
|
|
|
*fd_egress = r;
|
|
}
|
|
|
|
} else {
|
|
*fd_ingress = safe_close(*fd_ingress);
|
|
*fd_egress = safe_close(*fd_egress);
|
|
|
|
zero(u->ip_accounting_extra);
|
|
}
|
|
|
|
return 0;
|
|
}
|
|
|
|
int bpf_firewall_compile(Unit *u) {
|
|
CGroupContext *cc;
|
|
int r, supported;
|
|
bool ip_allow_any = false, ip_deny_any = false;
|
|
|
|
assert(u);
|
|
|
|
cc = unit_get_cgroup_context(u);
|
|
if (!cc)
|
|
return -EINVAL;
|
|
|
|
supported = bpf_firewall_supported();
|
|
if (supported < 0)
|
|
return supported;
|
|
if (supported == BPF_FIREWALL_UNSUPPORTED)
|
|
return log_unit_debug_errno(u, SYNTHETIC_ERRNO(EOPNOTSUPP),
|
|
"BPF firewalling not supported on this manager, proceeding without.");
|
|
if (supported != BPF_FIREWALL_SUPPORTED_WITH_MULTI && u->type == UNIT_SLICE)
|
|
/* If BPF_F_ALLOW_MULTI is not supported we don't support any BPF magic on inner nodes (i.e. on slice
|
|
* units), since that would mean leaf nodes couldn't do any BPF anymore at all. Under the assumption
|
|
* that BPF is more interesting on leaf nodes we hence avoid it on inner nodes in that case. This is
|
|
* consistent with old systemd behaviour from before v238, where BPF wasn't supported in inner nodes at
|
|
* all, either. */
|
|
return log_unit_debug_errno(u, SYNTHETIC_ERRNO(EOPNOTSUPP),
|
|
"BPF_F_ALLOW_MULTI is not supported on this manager, not doing BPF firewall on slice units.");
|
|
|
|
/* Note that when we compile a new firewall we first flush out the access maps and the BPF programs themselves,
|
|
* but we reuse the accounting maps. That way the firewall in effect always maps to the actual
|
|
* configuration, but we don't flush out the accounting unnecessarily */
|
|
|
|
u->ip_bpf_ingress = bpf_program_unref(u->ip_bpf_ingress);
|
|
u->ip_bpf_egress = bpf_program_unref(u->ip_bpf_egress);
|
|
|
|
u->ipv4_allow_map_fd = safe_close(u->ipv4_allow_map_fd);
|
|
u->ipv4_deny_map_fd = safe_close(u->ipv4_deny_map_fd);
|
|
|
|
u->ipv6_allow_map_fd = safe_close(u->ipv6_allow_map_fd);
|
|
u->ipv6_deny_map_fd = safe_close(u->ipv6_deny_map_fd);
|
|
|
|
if (u->type != UNIT_SLICE) {
|
|
/* In inner nodes we only do accounting, we do not actually bother with access control. However, leaf
|
|
* nodes will incorporate all IP access rules set on all their parent nodes. This has the benefit that
|
|
* they can optionally cancel out system-wide rules. Since inner nodes can't contain processes this
|
|
* means that all configure IP access rules *will* take effect on processes, even though we never
|
|
* compile them for inner nodes. */
|
|
|
|
r = bpf_firewall_prepare_access_maps(u, ACCESS_ALLOWED, &u->ipv4_allow_map_fd, &u->ipv6_allow_map_fd, &ip_allow_any);
|
|
if (r < 0)
|
|
return log_unit_error_errno(u, r, "Preparation of eBPF allow maps failed: %m");
|
|
|
|
r = bpf_firewall_prepare_access_maps(u, ACCESS_DENIED, &u->ipv4_deny_map_fd, &u->ipv6_deny_map_fd, &ip_deny_any);
|
|
if (r < 0)
|
|
return log_unit_error_errno(u, r, "Preparation of eBPF deny maps failed: %m");
|
|
}
|
|
|
|
r = bpf_firewall_prepare_accounting_maps(u, cc->ip_accounting, &u->ip_accounting_ingress_map_fd, &u->ip_accounting_egress_map_fd);
|
|
if (r < 0)
|
|
return log_unit_error_errno(u, r, "Preparation of eBPF accounting maps failed: %m");
|
|
|
|
r = bpf_firewall_compile_bpf(u, true, &u->ip_bpf_ingress, ip_allow_any, ip_deny_any);
|
|
if (r < 0)
|
|
return log_unit_error_errno(u, r, "Compilation for ingress BPF program failed: %m");
|
|
|
|
r = bpf_firewall_compile_bpf(u, false, &u->ip_bpf_egress, ip_allow_any, ip_deny_any);
|
|
if (r < 0)
|
|
return log_unit_error_errno(u, r, "Compilation for egress BPF program failed: %m");
|
|
|
|
return 0;
|
|
}
|
|
|
|
DEFINE_PRIVATE_HASH_OPS_WITH_VALUE_DESTRUCTOR(filter_prog_hash_ops, void, trivial_hash_func, trivial_compare_func, BPFProgram, bpf_program_unref);
|
|
|
|
static int load_bpf_progs_from_fs_to_set(Unit *u, char **filter_paths, Set **set) {
|
|
char **bpf_fs_path;
|
|
|
|
set_clear(*set);
|
|
|
|
STRV_FOREACH(bpf_fs_path, filter_paths) {
|
|
_cleanup_(bpf_program_unrefp) BPFProgram *prog = NULL;
|
|
int r;
|
|
|
|
r = bpf_program_new(BPF_PROG_TYPE_CGROUP_SKB, &prog);
|
|
if (r < 0)
|
|
return log_unit_error_errno(u, r, "Can't allocate CGROUP SKB BPF program: %m");
|
|
|
|
r = bpf_program_load_from_bpf_fs(prog, *bpf_fs_path);
|
|
if (r < 0)
|
|
return log_unit_error_errno(u, r, "Loading of ingress BPF program %s failed: %m", *bpf_fs_path);
|
|
|
|
r = set_ensure_consume(set, &filter_prog_hash_ops, TAKE_PTR(prog));
|
|
if (r < 0)
|
|
return log_unit_error_errno(u, r, "Can't add program to BPF program set: %m");
|
|
}
|
|
|
|
return 0;
|
|
}
|
|
|
|
int bpf_firewall_load_custom(Unit *u) {
|
|
CGroupContext *cc;
|
|
int r, supported;
|
|
|
|
assert(u);
|
|
|
|
cc = unit_get_cgroup_context(u);
|
|
if (!cc)
|
|
return 0;
|
|
|
|
if (!(cc->ip_filters_ingress || cc->ip_filters_egress))
|
|
return 0;
|
|
|
|
supported = bpf_firewall_supported();
|
|
if (supported < 0)
|
|
return supported;
|
|
|
|
if (supported != BPF_FIREWALL_SUPPORTED_WITH_MULTI)
|
|
return log_unit_debug_errno(u, SYNTHETIC_ERRNO(EOPNOTSUPP), "BPF_F_ALLOW_MULTI not supported on this manager, cannot attach custom BPF programs.");
|
|
|
|
r = load_bpf_progs_from_fs_to_set(u, cc->ip_filters_ingress, &u->ip_bpf_custom_ingress);
|
|
if (r < 0)
|
|
return r;
|
|
r = load_bpf_progs_from_fs_to_set(u, cc->ip_filters_egress, &u->ip_bpf_custom_egress);
|
|
if (r < 0)
|
|
return r;
|
|
|
|
return 0;
|
|
}
|
|
|
|
static int attach_custom_bpf_progs(Unit *u, const char *path, int attach_type, Set **set, Set **set_installed) {
|
|
BPFProgram *prog;
|
|
int r;
|
|
|
|
assert(u);
|
|
|
|
set_clear(*set_installed);
|
|
|
|
SET_FOREACH(prog, *set) {
|
|
r = bpf_program_cgroup_attach(prog, attach_type, path, BPF_F_ALLOW_MULTI);
|
|
if (r < 0)
|
|
return log_unit_error_errno(u, r, "Attaching custom egress BPF program to cgroup %s failed: %m", path);
|
|
|
|
/* Remember that these BPF programs are installed now. */
|
|
r = set_ensure_put(set_installed, &filter_prog_hash_ops, prog);
|
|
if (r < 0)
|
|
return log_unit_error_errno(u, r, "Can't add program to BPF program set: %m");
|
|
bpf_program_ref(prog);
|
|
}
|
|
|
|
return 0;
|
|
}
|
|
|
|
int bpf_firewall_install(Unit *u) {
|
|
_cleanup_free_ char *path = NULL;
|
|
CGroupContext *cc;
|
|
int r, supported;
|
|
uint32_t flags;
|
|
|
|
assert(u);
|
|
|
|
cc = unit_get_cgroup_context(u);
|
|
if (!cc)
|
|
return -EINVAL;
|
|
if (!u->cgroup_path)
|
|
return -EINVAL;
|
|
if (!u->cgroup_realized)
|
|
return -EINVAL;
|
|
|
|
supported = bpf_firewall_supported();
|
|
if (supported < 0)
|
|
return supported;
|
|
if (supported == BPF_FIREWALL_UNSUPPORTED) {
|
|
log_unit_debug(u, "BPF firewalling not supported on this manager, proceeding without.");
|
|
return -EOPNOTSUPP;
|
|
}
|
|
if (supported != BPF_FIREWALL_SUPPORTED_WITH_MULTI && u->type == UNIT_SLICE) {
|
|
log_unit_debug(u, "BPF_F_ALLOW_MULTI is not supported on this manager, not doing BPF firewall on slice units.");
|
|
return -EOPNOTSUPP;
|
|
}
|
|
if (supported != BPF_FIREWALL_SUPPORTED_WITH_MULTI &&
|
|
(!set_isempty(u->ip_bpf_custom_ingress) || !set_isempty(u->ip_bpf_custom_egress)))
|
|
return log_unit_debug_errno(u, SYNTHETIC_ERRNO(EOPNOTSUPP), "BPF_F_ALLOW_MULTI not supported on this manager, cannot attach custom BPF programs.");
|
|
|
|
r = cg_get_path(SYSTEMD_CGROUP_CONTROLLER, u->cgroup_path, NULL, &path);
|
|
if (r < 0)
|
|
return log_unit_error_errno(u, r, "Failed to determine cgroup path: %m");
|
|
|
|
flags = (supported == BPF_FIREWALL_SUPPORTED_WITH_MULTI &&
|
|
(u->type == UNIT_SLICE || unit_cgroup_delegate(u))) ? BPF_F_ALLOW_MULTI : 0;
|
|
|
|
/* Unref the old BPF program (which will implicitly detach it) right before attaching the new program, to
|
|
* minimize the time window when we don't account for IP traffic. */
|
|
u->ip_bpf_egress_installed = bpf_program_unref(u->ip_bpf_egress_installed);
|
|
u->ip_bpf_ingress_installed = bpf_program_unref(u->ip_bpf_ingress_installed);
|
|
|
|
if (u->ip_bpf_egress) {
|
|
r = bpf_program_cgroup_attach(u->ip_bpf_egress, BPF_CGROUP_INET_EGRESS, path,
|
|
flags | (set_isempty(u->ip_bpf_custom_egress) ? 0 : BPF_F_ALLOW_MULTI));
|
|
if (r < 0)
|
|
return log_unit_error_errno(u, r, "Attaching egress BPF program to cgroup %s failed: %m", path);
|
|
|
|
/* Remember that this BPF program is installed now. */
|
|
u->ip_bpf_egress_installed = bpf_program_ref(u->ip_bpf_egress);
|
|
}
|
|
|
|
if (u->ip_bpf_ingress) {
|
|
r = bpf_program_cgroup_attach(u->ip_bpf_ingress, BPF_CGROUP_INET_INGRESS, path,
|
|
flags | (set_isempty(u->ip_bpf_custom_ingress) ? 0 : BPF_F_ALLOW_MULTI));
|
|
if (r < 0)
|
|
return log_unit_error_errno(u, r, "Attaching ingress BPF program to cgroup %s failed: %m", path);
|
|
|
|
u->ip_bpf_ingress_installed = bpf_program_ref(u->ip_bpf_ingress);
|
|
}
|
|
|
|
r = attach_custom_bpf_progs(u, path, BPF_CGROUP_INET_EGRESS, &u->ip_bpf_custom_egress, &u->ip_bpf_custom_egress_installed);
|
|
if (r < 0)
|
|
return r;
|
|
|
|
r = attach_custom_bpf_progs(u, path, BPF_CGROUP_INET_INGRESS, &u->ip_bpf_custom_ingress, &u->ip_bpf_custom_ingress_installed);
|
|
if (r < 0)
|
|
return r;
|
|
|
|
return 0;
|
|
}
|
|
|
|
int bpf_firewall_read_accounting(int map_fd, uint64_t *ret_bytes, uint64_t *ret_packets) {
|
|
uint64_t key, packets;
|
|
int r;
|
|
|
|
if (map_fd < 0)
|
|
return -EBADF;
|
|
|
|
if (ret_packets) {
|
|
key = MAP_KEY_PACKETS;
|
|
r = bpf_map_lookup_element(map_fd, &key, &packets);
|
|
if (r < 0)
|
|
return r;
|
|
}
|
|
|
|
if (ret_bytes) {
|
|
key = MAP_KEY_BYTES;
|
|
r = bpf_map_lookup_element(map_fd, &key, ret_bytes);
|
|
if (r < 0)
|
|
return r;
|
|
}
|
|
|
|
if (ret_packets)
|
|
*ret_packets = packets;
|
|
|
|
return 0;
|
|
}
|
|
|
|
int bpf_firewall_reset_accounting(int map_fd) {
|
|
uint64_t key, value = 0;
|
|
int r;
|
|
|
|
if (map_fd < 0)
|
|
return -EBADF;
|
|
|
|
key = MAP_KEY_PACKETS;
|
|
r = bpf_map_update_element(map_fd, &key, &value);
|
|
if (r < 0)
|
|
return r;
|
|
|
|
key = MAP_KEY_BYTES;
|
|
return bpf_map_update_element(map_fd, &key, &value);
|
|
}
|
|
|
|
static int bpf_firewall_unsupported_reason = 0;
|
|
|
|
int bpf_firewall_supported(void) {
|
|
const struct bpf_insn trivial[] = {
|
|
BPF_MOV64_IMM(BPF_REG_0, 1),
|
|
BPF_EXIT_INSN()
|
|
};
|
|
|
|
_cleanup_(bpf_program_unrefp) BPFProgram *program = NULL;
|
|
static int supported = -1;
|
|
union bpf_attr attr;
|
|
int r;
|
|
|
|
/* Checks whether BPF firewalling is supported. For this, we check the following things:
|
|
*
|
|
* - whether the unified hierarchy is being used
|
|
* - the BPF implementation in the kernel supports BPF_PROG_TYPE_CGROUP_SKB programs, which we require
|
|
* - the BPF implementation in the kernel supports the BPF_PROG_DETACH call, which we require
|
|
*/
|
|
if (supported >= 0)
|
|
return supported;
|
|
|
|
r = cg_unified_controller(SYSTEMD_CGROUP_CONTROLLER);
|
|
if (r < 0)
|
|
return log_error_errno(r, "Can't determine whether the unified hierarchy is used: %m");
|
|
if (r == 0) {
|
|
bpf_firewall_unsupported_reason =
|
|
log_debug_errno(SYNTHETIC_ERRNO(EUCLEAN),
|
|
"Not running with unified cgroups, BPF firewalling is not supported.");
|
|
return supported = BPF_FIREWALL_UNSUPPORTED;
|
|
}
|
|
|
|
r = bpf_program_new(BPF_PROG_TYPE_CGROUP_SKB, &program);
|
|
if (r < 0) {
|
|
bpf_firewall_unsupported_reason =
|
|
log_debug_errno(r, "Can't allocate CGROUP SKB BPF program, BPF firewalling is not supported: %m");
|
|
return supported = BPF_FIREWALL_UNSUPPORTED;
|
|
}
|
|
|
|
r = bpf_program_add_instructions(program, trivial, ELEMENTSOF(trivial));
|
|
if (r < 0) {
|
|
bpf_firewall_unsupported_reason =
|
|
log_debug_errno(r, "Can't add trivial instructions to CGROUP SKB BPF program, BPF firewalling is not supported: %m");
|
|
return supported = BPF_FIREWALL_UNSUPPORTED;
|
|
}
|
|
|
|
r = bpf_program_load_kernel(program, NULL, 0);
|
|
if (r < 0) {
|
|
bpf_firewall_unsupported_reason =
|
|
log_debug_errno(r, "Can't load kernel CGROUP SKB BPF program, BPF firewalling is not supported: %m");
|
|
return supported = BPF_FIREWALL_UNSUPPORTED;
|
|
}
|
|
|
|
/* Unfortunately the kernel allows us to create BPF_PROG_TYPE_CGROUP_SKB programs even when CONFIG_CGROUP_BPF
|
|
* is turned off at kernel compilation time. This sucks of course: why does it allow us to create a cgroup BPF
|
|
* program if we can't do a thing with it later?
|
|
*
|
|
* We detect this case by issuing the BPF_PROG_DETACH bpf() call with invalid file descriptors: if
|
|
* CONFIG_CGROUP_BPF is turned off, then the call will fail early with EINVAL. If it is turned on the
|
|
* parameters are validated however, and that'll fail with EBADF then. */
|
|
|
|
attr = (union bpf_attr) {
|
|
.attach_type = BPF_CGROUP_INET_EGRESS,
|
|
.target_fd = -1,
|
|
.attach_bpf_fd = -1,
|
|
};
|
|
|
|
if (bpf(BPF_PROG_DETACH, &attr, sizeof(attr)) < 0) {
|
|
if (errno != EBADF) {
|
|
bpf_firewall_unsupported_reason =
|
|
log_debug_errno(errno, "Didn't get EBADF from BPF_PROG_DETACH, BPF firewalling is not supported: %m");
|
|
return supported = BPF_FIREWALL_UNSUPPORTED;
|
|
}
|
|
|
|
/* YAY! */
|
|
} else {
|
|
log_debug("Wut? Kernel accepted our invalid BPF_PROG_DETACH call? Something is weird, assuming BPF firewalling is broken and hence not supported.");
|
|
return supported = BPF_FIREWALL_UNSUPPORTED;
|
|
}
|
|
|
|
/* So now we know that the BPF program is generally available, let's see if BPF_F_ALLOW_MULTI is also supported
|
|
* (which was added in kernel 4.15). We use a similar logic as before, but this time we use the BPF_PROG_ATTACH
|
|
* bpf() call and the BPF_F_ALLOW_MULTI flags value. Since the flags are checked early in the system call we'll
|
|
* get EINVAL if it's not supported, and EBADF as before if it is available. */
|
|
|
|
attr = (union bpf_attr) {
|
|
.attach_type = BPF_CGROUP_INET_EGRESS,
|
|
.target_fd = -1,
|
|
.attach_bpf_fd = -1,
|
|
.attach_flags = BPF_F_ALLOW_MULTI,
|
|
};
|
|
|
|
if (bpf(BPF_PROG_ATTACH, &attr, sizeof(attr)) < 0) {
|
|
if (errno == EBADF) {
|
|
log_debug_errno(errno, "Got EBADF when using BPF_F_ALLOW_MULTI, which indicates it is supported. Yay!");
|
|
return supported = BPF_FIREWALL_SUPPORTED_WITH_MULTI;
|
|
}
|
|
|
|
if (errno == EINVAL)
|
|
log_debug_errno(errno, "Got EINVAL error when using BPF_F_ALLOW_MULTI, which indicates it's not supported.");
|
|
else
|
|
log_debug_errno(errno, "Got unexpected error when using BPF_F_ALLOW_MULTI, assuming it's not supported: %m");
|
|
|
|
return supported = BPF_FIREWALL_SUPPORTED;
|
|
} else {
|
|
log_debug("Wut? Kernel accepted our invalid BPF_PROG_ATTACH+BPF_F_ALLOW_MULTI call? Something is weird, assuming BPF firewalling is broken and hence not supported.");
|
|
return supported = BPF_FIREWALL_UNSUPPORTED;
|
|
}
|
|
}
|
|
|
|
void emit_bpf_firewall_warning(Unit *u) {
|
|
static bool warned = false;
|
|
|
|
if (!warned) {
|
|
bool quiet = bpf_firewall_unsupported_reason == -EPERM && detect_container();
|
|
|
|
log_unit_full_errno(u, quiet ? LOG_DEBUG : LOG_WARNING, bpf_firewall_unsupported_reason,
|
|
"unit configures an IP firewall, but %s.\n"
|
|
"(This warning is only shown for the first unit using IP firewalling.)",
|
|
getuid() != 0 ? "not running as root" :
|
|
"the local system does not support BPF/cgroup firewalling");
|
|
warned = true;
|
|
}
|
|
}
|