411543949
Zhou Siqi
2025-02-09
Subject
udhcpc6: generate a consistent IAID
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networking/udhcp/d6_dhcpc.c+27 -2
| @@ -622,6 +622,31 @@ static NOINLINE int send_d6_info_request(void) | |
| return d6_mcast_from_client_data_ifindex(&packet, opt_ptr); | |
| } | |
| + | /* |
| + | * RFC 3315 10. Identity Association |
| + | * |
| + | * An "identity-association" (IA) is a construct through which a server |
| + | * and a client can identify, group, and manage a set of related IPv6 |
| + | * addresses. Each IA consists of an IAID and associated configuration |
| + | * information. |
| + | * |
| + | * A client must associate at least one distinct IA with each of its |
| + | * network interfaces for which it is to request the assignment of IPv6 |
| + | * addresses from a DHCP server. The client uses the IAs assigned to an |
| + | * interface to obtain configuration information from a server for that |
| + | * interface. Each IA must be associated with exactly one interface. |
| + | * |
| + | * The IAID uniquely identifies the IA and must be chosen to be unique |
| + | * among the IAIDs on the client. The IAID is chosen by the client. |
| + | * For any given use of an IA by the client, the IAID for that IA MUST |
| + | * be consistent across restarts of the DHCP client... |
| + | */ |
| + | /* Generate IAID. We base it on our MAC address' last 4 bytes */ |
| + | static void generate_iaid(uint8_t *iaid) |
| + | { |
| + | memcpy(iaid, &client_data.client_mac[2], 4); |
| + | } |
| + | |
| /* Multicast a DHCPv6 Solicit packet to the network, with an optionally requested IP. | |
| * | |
| * RFC 3315 17.1.1. Creation of Solicit Messages | |
| @@ -721,7 +746,7 @@ static NOINLINE int send_d6_discover(struct in6_addr *requested_ipv6) | |
| client6_data.ia_na = xzalloc(len); | |
| client6_data.ia_na->code = D6_OPT_IA_NA; | |
| client6_data.ia_na->len = len - 4; | |
| - | *(bb__aliased_uint32_t*)client6_data.ia_na->data = rand(); /* IAID */ |
| + | generate_iaid(client6_data.ia_na->data); /* IAID */ |
| if (requested_ipv6) { | |
| struct d6_option *iaaddr = (void*)(client6_data.ia_na->data + 4+4+4); | |
| iaaddr->code = D6_OPT_IAADDR; | |
| @@ -739,7 +764,7 @@ static NOINLINE int send_d6_discover(struct in6_addr *requested_ipv6) | |
| client6_data.ia_pd = xzalloc(len); | |
| client6_data.ia_pd->code = D6_OPT_IA_PD; | |
| client6_data.ia_pd->len = len - 4; | |
| - | *(bb__aliased_uint32_t*)client6_data.ia_pd->data = rand(); /* IAID */ |
| + | generate_iaid(client6_data.ia_na->data); /* IAID */ |
| opt_ptr = mempcpy(opt_ptr, client6_data.ia_pd, len); | |
| } | |