BPF_STMT(BPF_LD + BPF_B + BPF_ABS, offsetof(DHCPPacket, dhcp.htype)), /* A <- DHCP header type */
BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, arp_type, 1, 0), /* header type == arp_type ? */
BPF_STMT(BPF_RET + BPF_K, 0), /* ignore */
- BPF_STMT(BPF_LD + BPF_B + BPF_ABS, offsetof(DHCPPacket, dhcp.hlen)), /* A <- MAC address length */
- BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, dhcp_hlen, 1, 0), /* address length == dhcp_hlen ? */
- BPF_STMT(BPF_RET + BPF_K, 0), /* ignore */
BPF_STMT(BPF_LD + BPF_W + BPF_ABS, offsetof(DHCPPacket, dhcp.xid)), /* A <- client identifier */
BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, xid, 1, 0), /* client identifier == xid ? */
BPF_STMT(BPF_RET + BPF_K, 0), /* ignore */
+ BPF_STMT(BPF_LD + BPF_B + BPF_ABS, offsetof(DHCPPacket, dhcp.hlen)), /* A <- MAC address length */
+ BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, dhcp_hlen, 1, 0), /* address length == dhcp_hlen ? */
+ BPF_STMT(BPF_RET + BPF_K, 0), /* ignore */
+
+ /* We only support MAC address length to be either 0 or 6 (ETH_ALEN). Optionally
+ * compare chaddr for ETH_ALEN bytes. */
+ BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, ETH_ALEN, 0, 12), /* A (the MAC address length) == ETH_ALEN ? */
BPF_STMT(BPF_LD + BPF_IMM, unaligned_read_be32(ð_mac->ether_addr_octet[0])), /* A <- 4 bytes of client's MAC */
BPF_STMT(BPF_MISC + BPF_TAX, 0), /* X <- A */
BPF_STMT(BPF_LD + BPF_W + BPF_ABS, offsetof(DHCPPacket, dhcp.chaddr)), /* A <- 4 bytes of MAC from dhcp.chaddr */
BPF_STMT(BPF_ALU + BPF_XOR + BPF_X, 0), /* A xor X */
BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, 0, 1, 0), /* A == 0 ? */
BPF_STMT(BPF_RET + BPF_K, 0), /* ignore */
+
BPF_STMT(BPF_LD + BPF_W + BPF_ABS, offsetof(DHCPPacket, dhcp.magic)), /* A <- DHCP magic cookie */
BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, DHCP_MAGIC_COOKIE, 1, 0), /* cookie == DHCP magic cookie ? */
BPF_STMT(BPF_RET + BPF_K, 0), /* ignore */
sd_dhcp_client *client = userdata;
_cleanup_free_ DHCPMessage *message = NULL;
- const struct ether_addr zero_mac = {};
- const struct ether_addr *expected_chaddr = NULL;
+ const uint8_t *expected_chaddr = NULL;
uint8_t expected_hlen = 0;
ssize_t len, buflen;
if (client->arp_type == ARPHRD_ETHER) {
expected_hlen = ETH_ALEN;
- expected_chaddr = (const struct ether_addr *) &client->mac_addr;
- } else {
- /* Non-Ethernet links expect zero chaddr */
- expected_hlen = 0;
- expected_chaddr = &zero_mac;
+ expected_chaddr = &client->mac_addr[0];
}
if (message->hlen != expected_hlen) {
return 0;
}
- if (memcmp(&message->chaddr[0], expected_chaddr, ETH_ALEN)) {
+ if (expected_hlen > 0 && memcmp(&message->chaddr[0], expected_chaddr, expected_hlen)) {
log_dhcp_client(client, "Received chaddr does not match expected: ignoring");
return 0;
}