dhcpv4: remove some magic numbers

Add a bunch of #define's to dhcpv4.h and use the defined constants to reduce
the number of magic constants.

Signed-off-by: David Härdeman <[email protected]>
Link: https://github.com/openwrt/odhcpd/pull/266
Signed-off-by: Álvaro Fernández Rojas <[email protected]>

diff --git a/src/dhcpv4.c b/src/dhcpv4.c
index 2dd4b3a205631332396afa75c8946c3ea9dc858b..733ab4ad7b0065e80827868b009851dd49e65947 100644 (file)
--- a/src/dhcpv4.c
+++ b/src/dhcpv4.c
@@ -157,42 +157,38 @@ static void dhcpv4_put(struct dhcpv4_message *msg, uint8_t **cookie,
 static void dhcpv4_fr_send(struct dhcp_assignment *a)
 {
        struct dhcpv4_message fr_msg = {
-               .op = DHCPV4_BOOTREPLY,
-               .htype = 1,
-               .hlen = 6,
+               .op = DHCPV4_OP_BOOTREPLY,
+               .htype = ARPHRD_ETHER,
+               .hlen = ETH_ALEN,
                .hops = 0,
                .secs = 0,
                .flags = 0,
-               .ciaddr = {INADDR_ANY},
-               .yiaddr = {INADDR_ANY},
-               .siaddr = {INADDR_ANY},
-               .giaddr = {INADDR_ANY},
-               .chaddr = {0},
-               .sname = {0},
-               .file = {0},
+               .ciaddr = { INADDR_ANY },
+               .yiaddr = { INADDR_ANY },
+               .siaddr = { INADDR_ANY },
+               .giaddr = { INADDR_ANY },
+               .chaddr = { 0 },
+               .sname = { 0 },
+               .file = { 0 },
+               .options = { DHCPV4_MAGIC_COOKIE },
        };
        struct dhcpv4_auth_forcerenew *auth_o, auth = {
-               .protocol = 3,
-               .algorithm = 1,
-               .rdm = 0,
-               .replay = {htonl(time(NULL)), htonl(++serial)},
-               .type = 2,
-               .key = {0},
+               .protocol = DHCPV4_AUTH_PROTO_RKAP,
+               .algorithm = DHCPV4_AUTH_ALG_HMAC_MD5,
+               .rdm = DHCPV4_AUTH_RDM_MONOTONIC,
+               .replay = { htonl(time(NULL)), htonl(++serial) },
+               .type = DHCPV4_AUTH_RKAP_AI_TYPE_MD5_DIGEST,
+               .key = { 0 },
        };
        struct interface *iface = a->iface;
 
        odhcpd_urandom(&fr_msg.xid, sizeof(fr_msg.xid));
        memcpy(fr_msg.chaddr, a->hwaddr, fr_msg.hlen);
 
-       fr_msg.options[0] = 0x63;
-       fr_msg.options[1] = 0x82;
-       fr_msg.options[2] = 0x53;
-       fr_msg.options[3] = 0x63;
-
-       uint8_t *cookie = &fr_msg.options[4];
+       uint8_t *cookie = &fr_msg.options[DHCPV4_MAGIC_COOKIE_LEN];
        uint8_t msg = DHCPV4_MSG_FORCERENEW;
 
-       dhcpv4_put(&fr_msg, &cookie, DHCPV4_OPT_MESSAGE, 1, &msg);
+       dhcpv4_put(&fr_msg, &cookie, DHCPV4_OPT_MESSAGE, sizeof(msg), &msg);
        if (a->accept_fr_nonce) {
                dhcpv4_put(&fr_msg, &cookie, DHCPV4_OPT_AUTHENTICATION, sizeof(auth), &auth);
                auth_o = (struct dhcpv4_auth_forcerenew *)(cookie - sizeof(auth));
@@ -571,7 +567,7 @@ void dhcpv4_handle_msg(void *addr, void *data, size_t len,
                return;
 
        if (len < offsetof(struct dhcpv4_message, options) + 4 ||
-                       req->op != DHCPV4_BOOTREQUEST || req->hlen != 6)
+                       req->op != DHCPV4_OP_BOOTREQUEST || req->hlen != ETH_ALEN)
                return;
 
        syslog(LOG_DEBUG, "Got DHCPv4 request on %s", iface->name);
@@ -584,25 +580,21 @@ void dhcpv4_handle_msg(void *addr, void *data, size_t len,
        int sock = iface->dhcpv4_event.uloop.fd;
 
        struct dhcpv4_message reply = {
-               .op = DHCPV4_BOOTREPLY,
+               .op = DHCPV4_OP_BOOTREPLY,
                .htype = req->htype,
                .hlen = req->hlen,
                .hops = 0,
                .xid = req->xid,
                .secs = 0,
                .flags = req->flags,
-               .ciaddr = {INADDR_ANY},
+               .ciaddr = { INADDR_ANY },
                .giaddr = req->giaddr,
                .siaddr = iface->dhcpv4_local,
+               .options = { DHCPV4_MAGIC_COOKIE },
        };
        memcpy(reply.chaddr, req->chaddr, sizeof(reply.chaddr));
 
-       reply.options[0] = 0x63;
-       reply.options[1] = 0x82;
-       reply.options[2] = 0x53;
-       reply.options[3] = 0x63;
-
-       uint8_t *cookie = &reply.options[4];
+       uint8_t *cookie = &reply.options[DHCPV4_MAGIC_COOKIE_LEN];
        uint8_t reqmsg = DHCPV4_MSG_REQUEST;
        uint8_t msg = DHCPV4_MSG_ACK;
 
@@ -750,12 +742,12 @@ void dhcpv4_handle_msg(void *addr, void *data, size_t len,
                if (incl_fr_opt) {
                        if (reqmsg == DHCPV4_MSG_REQUEST) {
                                struct dhcpv4_auth_forcerenew auth = {
-                                       .protocol = 3,
-                                       .algorithm = 1,
-                                       .rdm = 0,
-                                       .replay = {htonl(time(NULL)), htonl(++serial)},
-                                       .type = 1,
-                                       .key = {0},
+                                       .protocol = DHCPV4_AUTH_PROTO_RKAP,
+                                       .algorithm = DHCPV4_AUTH_ALG_HMAC_MD5,
+                                       .rdm = DHCPV4_AUTH_RDM_MONOTONIC,
+                                       .replay = { htonl(time(NULL)), htonl(++serial) },
+                                       .type = DHCPV4_AUTH_RKAP_AI_TYPE_KEY,
+                                       .key = { 0 },
                                };
 
                                memcpy(auth.key, a->key, sizeof(auth.key));

diff --git a/src/dhcpv4.h b/src/dhcpv4.h
index dd3fc51288d39af0d680f63b5486d7aceb0dc9f0..36fc1a79a936339294ad326e2e2045575268bb7a 100644 (file)
--- a/src/dhcpv4.h
+++ b/src/dhcpv4.h
@@ -25,8 +25,8 @@
 #define DHCPV4_FR_MAX_FUZZ     500
 
 enum dhcpv4_op {
-       DHCPV4_BOOTREQUEST = 1,
-       DHCPV4_BOOTREPLY = 2
+       DHCPV4_OP_BOOTREQUEST = 1,
+       DHCPV4_OP_BOOTREPLY = 2,
 };
 
 // https://www.iana.org/assignments/bootp-dhcp-parameters/bootp-dhcp-parameters.xhtml#message-type-53
@@ -95,6 +95,11 @@ struct dhcpv4_message {
        uint8_t options[312];
 };
 
+// RFC2131, §3
+#define DHCPV4_MAGIC_COOKIE 99, 130, 83, 99
+#define DHCPV4_MAGIC_COOKIE_LEN 4
+
+// RFC3203, §6; RFC3118, §2; RFC6704, §3.1.2
 struct dhcpv4_auth_forcerenew {
        uint8_t protocol;
        uint8_t algorithm;
@@ -104,6 +109,32 @@ struct dhcpv4_auth_forcerenew {
        uint8_t key[16];
 } _packed;
 
+// https://www.iana.org/assignments/auth-namespaces/auth-namespaces.xhtml#auth-namespaces-1
+enum dhcpv4_auth_protocol {
+       DHCPV4_AUTH_PROTO_CFG_TOKEN     =       0,      // RFC3118
+       DHCPV4_AUTH_PROTO_DELAYED       =       1,      // RFC3118
+       DHCPV4_AUTH_PROTO_DELAYED_OBS   =       2,      // RFC8415, Obsolete
+       DHCPV4_AUTH_PROTO_RKAP          =       3,      // RFC8415, also RFC6704
+       DHCPV4_AUTH_PROTO_SPLIT_DNS     =       4,      // RFC9704
+};
+
+// https://www.iana.org/assignments/auth-namespaces/auth-namespaces.xhtml#auth-namespaces-2
+enum dhcpv4_auth_algorithm {
+       DHCPV4_AUTH_ALG_CFG_TOKEN       =       0,      // RFC3118
+       DHCPV4_AUTH_ALG_HMAC_MD5        =       1,      // RFC3118, RFC8415, also RFC6704
+};
+
+// https://www.iana.org/assignments/auth-namespaces/auth-namespaces.xhtml#auth-namespaces-2
+enum dhcpv4_auth_rdm {
+       DHCPV4_AUTH_RDM_MONOTONIC       =       0,      // RFC3118, RFC8415, also RFC6704
+};
+
+// RFC6704, §3.1.2 (for DHCPv6: RFC8415, §20.4)
+enum dhcpv4_auth_rkap_ai_type {
+       DHCPV4_AUTH_RKAP_AI_TYPE_KEY            =       1,
+       DHCPV4_AUTH_RKAP_AI_TYPE_MD5_DIGEST     =       2,
+};
+
 struct dhcpv4_option {
        uint8_t type;
        uint8_t len;