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arp-util: shorten BPF code a bit
- replace `A = k` and `X = A` with `X = k`, - replace `A ^= X` and `A == 0` with `A == X`. - use UINT32_MAX when accept a packet
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@ -14,7 +14,7 @@
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#include "unaligned.h"
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#include "util.h"
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int arp_update_filter(int fd, const struct in_addr *a, const struct ether_addr *eth_mac) {
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int arp_update_filter(int fd, const struct in_addr *a, const struct ether_addr *mac) {
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struct sock_filter filter[] = {
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BPF_STMT(BPF_LD + BPF_W + BPF_LEN, 0), /* A <- packet length */
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BPF_JUMP(BPF_JMP + BPF_JGE + BPF_K, sizeof(struct ether_arp), 1, 0), /* packet >= arp packet ? */
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@ -36,30 +36,22 @@ int arp_update_filter(int fd, const struct in_addr *a, const struct ether_addr *
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BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, ARPOP_REPLY, 1, 0), /* protocol == reply ? */
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BPF_STMT(BPF_RET + BPF_K, 0), /* ignore */
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/* Sender Hardware Address must be different from our own */
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BPF_STMT(BPF_LD + BPF_IMM, unaligned_read_be32(ð_mac->ether_addr_octet[0])),/* A <- 4 bytes of client's MAC */
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BPF_STMT(BPF_MISC + BPF_TAX, 0), /* X <- A */
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BPF_STMT(BPF_LDX + BPF_IMM, unaligned_read_be32(&mac->ether_addr_octet[0])), /* X <- 4 bytes of client's MAC */
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BPF_STMT(BPF_LD + BPF_W + BPF_ABS, offsetof(struct ether_arp, arp_sha)), /* A <- 4 bytes of SHA */
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BPF_STMT(BPF_ALU + BPF_XOR + BPF_X, 0), /* A xor X */
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BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, 0, 0, 6), /* A == 0 ? */
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BPF_STMT(BPF_LD + BPF_IMM, unaligned_read_be16(ð_mac->ether_addr_octet[4])),/* A <- remainder of client's MAC */
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BPF_STMT(BPF_MISC + BPF_TAX, 0), /* X <- A */
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BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_X, 0, 0, 4), /* A == X ? */
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BPF_STMT(BPF_LDX + BPF_IMM, unaligned_read_be16(&mac->ether_addr_octet[4])), /* X <- remainder of client's MAC */
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BPF_STMT(BPF_LD + BPF_H + BPF_ABS, offsetof(struct ether_arp, arp_sha) + 4), /* A <- remainder of SHA */
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BPF_STMT(BPF_ALU + BPF_XOR + BPF_X, 0), /* A xor X */
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BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, 0, 0, 1), /* A == 0 ? */
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BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_X, 0, 0, 1), /* A == X ? */
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BPF_STMT(BPF_RET + BPF_K, 0), /* ignore */
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/* Sender Protocol Address or Target Protocol Address must be equal to the one we care about */
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BPF_STMT(BPF_LD + BPF_IMM, htobe32(a->s_addr)), /* A <- clients IP */
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BPF_STMT(BPF_MISC + BPF_TAX, 0), /* X <- A */
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BPF_STMT(BPF_LDX + BPF_IMM, htobe32(a->s_addr)), /* X <- clients IP */
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BPF_STMT(BPF_LD + BPF_W + BPF_ABS, offsetof(struct ether_arp, arp_spa)), /* A <- SPA */
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BPF_STMT(BPF_ALU + BPF_XOR + BPF_X, 0), /* X xor A */
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BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, 0, 0, 1), /* A == 0 ? */
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BPF_STMT(BPF_RET + BPF_K, 65535), /* return all */
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BPF_STMT(BPF_LD + BPF_IMM, htobe32(a->s_addr)), /* A <- clients IP */
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BPF_STMT(BPF_MISC + BPF_TAX, 0), /* X <- A */
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BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_X, 0, 0, 1), /* A == X ? */
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BPF_STMT(BPF_RET + BPF_K, UINT32_MAX), /* accept */
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BPF_STMT(BPF_LDX + BPF_IMM, htobe32(a->s_addr)), /* A <- clients IP */
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BPF_STMT(BPF_LD + BPF_W + BPF_ABS, offsetof(struct ether_arp, arp_tpa)), /* A <- TPA */
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BPF_STMT(BPF_ALU + BPF_XOR + BPF_X, 0), /* X xor A */
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BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, 0, 0, 1), /* A == 0 ? */
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BPF_STMT(BPF_RET + BPF_K, 65535), /* return all */
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BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_X, 0, 0, 1), /* A == 0 ? */
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BPF_STMT(BPF_RET + BPF_K, UINT32_MAX), /* accept */
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BPF_STMT(BPF_RET + BPF_K, 0), /* ignore */
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};
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struct sock_fprog fprog = {
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@ -75,7 +67,7 @@ int arp_update_filter(int fd, const struct in_addr *a, const struct ether_addr *
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return 0;
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}
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int arp_network_bind_raw_socket(int ifindex, const struct in_addr *a, const struct ether_addr *eth_mac) {
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int arp_network_bind_raw_socket(int ifindex, const struct in_addr *a, const struct ether_addr *mac) {
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union sockaddr_union link = {
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.ll.sll_family = AF_PACKET,
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.ll.sll_protocol = htobe16(ETH_P_ARP),
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@ -87,12 +79,13 @@ int arp_network_bind_raw_socket(int ifindex, const struct in_addr *a, const stru
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int r;
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assert(ifindex > 0);
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assert(mac);
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s = socket(AF_PACKET, SOCK_DGRAM | SOCK_CLOEXEC | SOCK_NONBLOCK, 0);
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if (s < 0)
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return -errno;
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r = arp_update_filter(s, a, eth_mac);
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r = arp_update_filter(s, a, mac);
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if (r < 0)
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return r;
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@ -11,8 +11,8 @@
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#include "socket-util.h"
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#include "sparse-endian.h"
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int arp_update_filter(int fd, const struct in_addr *a, const struct ether_addr *eth_mac);
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int arp_network_bind_raw_socket(int ifindex, const struct in_addr *a, const struct ether_addr *eth_mac);
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int arp_update_filter(int fd, const struct in_addr *a, const struct ether_addr *mac);
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int arp_network_bind_raw_socket(int ifindex, const struct in_addr *a, const struct ether_addr *mac);
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int arp_send_packet(
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int fd,
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