libdhcp: Reduce stack use

2 files changed, 39 insertions, 33 deletions

diff --git a/build-aux/stack.c.gen b/build-aux/stack.c.gen
index ae05a78..97775a6 100755
--- a/build-aux/stack.c.gen
+++ b/build-aux/stack.c.gen
@@ -209,7 +209,10 @@ def main(ci_fnames: list[str]) -> None:
 
     print("/*")
 
+    dbg = False
+
     def nstatic(funcname: str, chain: list[str] = []) -> int:
+        nonlocal dbg
         if funcname not in graph:
             if f"__wrap_{funcname}" in graph:
                 # Handle `ld --wrap` functions
@@ -224,6 +227,8 @@ def main(ci_fnames: list[str]) -> None:
             cycles.add(f"{chain[chain.index(funcname):] + [funcname]}")
             return 9999999
         node = graph[funcname]
+        if dbg:
+            print(f"//dbg: {funcname}\t{node.nstatic}")
         return node.nstatic + max(
             [0, *[nstatic(call, chain + [funcname]) for call in node.calls]]
         )
@@ -234,6 +239,7 @@ def main(ci_fnames: list[str]) -> None:
 
     for funcname in graph:
         if funcname.endswith("_cr"):
+            # dbg = "dhcp" in funcname
             print(f"{funcname.ljust(namelen)} {str(nstatic(funcname)).rjust(numlen)}")
 
     print(("=" * namelen) + " " + "=" * numlen)
diff --git a/libdhcp/dhcp_client.c b/libdhcp/dhcp_client.c
index dad039c..3673d2c 100644
--- a/libdhcp/dhcp_client.c
+++ b/libdhcp/dhcp_client.c
@@ -188,23 +188,23 @@ static inline enum requirement dhcp_table5(typeof((struct dhcp_client){}.state)
 	/* Encode "Table 5: Fields and options used by DHCP clients"
 	 * from
 	 * https://datatracker.ietf.org/doc/html/rfc2131#page-38.  */
-#define INC_ADDR ({	  \
-			enum requirement req; \
-			switch (state) { \
-			case STATE_SELECTING: case STATE_INIT_REBOOT: req = MUST;     break; \
-			case STATE_BOUND: case STATE_RENEWING:        req = MUST_NOT; break; \
+#define INC_ADDR ({                                                                             \
+			enum requirement req;                                                   \
+			switch (state) {                                                        \
+			case STATE_SELECTING: case STATE_INIT_REBOOT: req = MUST;     break;    \
+			case STATE_BOUND: case STATE_RENEWING:        req = MUST_NOT; break;    \
 			case IMPOSSIBLE_REQUEST_STATES: default:      req = _SHOULD_NOT_HAPPEN; \
-			} \
-			req; \
+			}                                                                       \
+			req;                                                                    \
 		})
-#define INC_SERVER ({	  \
-			enum requirement req; \
-			switch (state) { \
-			case STATE_SELECTING:                                          req = MUST;     break; \
-			case STATE_INIT_REBOOT: case STATE_BOUND: case STATE_RENEWING: req = MUST_NOT; break; \
+#define INC_SERVER ({                                                                                            \
+			enum requirement req;                                                                    \
+			switch (state) {                                                                         \
+			case STATE_SELECTING:                                          req = MUST;     break;    \
+			case STATE_INIT_REBOOT: case STATE_BOUND: case STATE_RENEWING: req = MUST_NOT; break;    \
 			case IMPOSSIBLE_REQUEST_STATES: default:                       req = _SHOULD_NOT_HAPPEN; \
-			} \
-			req; \
+			}                                                                                        \
+			req;                                                                                     \
 		})
 	struct { enum requirement cols[5]; } row;
 #define ROW(...) row = (typeof(row)){{ __VA_ARGS__ }}
@@ -466,12 +466,12 @@ static bool dhcp_client_send(struct dhcp_client *client, uint8_t msgtyp, const c
 struct dhcp_recv_msg {
 	struct dhcp_msg         raw;
 	struct {
+		uint16_t                off;
 		uint16_t                len;
-		uint8_t                *dat;
-	}                       options[0x100];
-	uint8_t                 _option_data[sizeof((struct dhcp_msg){}.options)+
-	                                     sizeof((struct dhcp_msg){}.file)+
-	                                     sizeof((struct dhcp_msg){}.sname)];
+	}                       options[0xff];
+	uint8_t                 option_dat[sizeof((struct dhcp_msg){}.options)+
+	                                   sizeof((struct dhcp_msg){}.file)+
+	                                   sizeof((struct dhcp_msg){}.sname)];
 };
 
 /** @return whether there is an error */
@@ -513,7 +513,7 @@ static inline void _dhcp_client_recv_consolidate_opts(struct dhcp_recv_msg *ret,
 			break;
 		default:
 			opt_len = dat[pos++];
-			memcpy(&ret->options[opt_typ].dat[ret->options[opt_typ].len], &dat[pos], opt_len);
+			memcpy(&ret->option_dat[ret->options[opt_typ].off+ret->options[opt_typ].len], &dat[pos], opt_len);
 			ret->options[opt_typ].len += opt_len;
 		}
 	}
@@ -643,7 +643,7 @@ static ssize_t dhcp_client_recv(struct dhcp_client *client, struct dhcp_recv_msg
 			continue;
 		if (!dhcp_opt_length_is_valid(opt, ret->options[opt].len))
 			goto ignore;
-		ret->options[opt].dat = &ret->_option_data[allocated];
+		ret->options[opt].off = allocated;
 		allocated += ret->options[opt].len;
 		ret->options[opt].len = 0;
 	}
@@ -660,7 +660,7 @@ static ssize_t dhcp_client_recv(struct dhcp_client *client, struct dhcp_recv_msg
 		goto ignore;
 	for (uint8_t opt = 1; opt < 255; opt++) {
 		enum requirement req = dhcp_table3(client->last_sent_msgtyp,
-		                                   ret->options[DHCP_OPT_DHCP_MSG_TYPE].dat[0],
+		                                   ret->option_dat[ret->options[DHCP_OPT_DHCP_MSG_TYPE].off],
 		                                   opt);
 		switch (req) {
 		case MUST:
@@ -684,7 +684,7 @@ static ssize_t dhcp_client_recv(struct dhcp_client *client, struct dhcp_recv_msg
 	if (ret->options[DHCP_OPT_CLASS_ID].len) {
 		/* https://datatracker.ietf.org/doc/html/rfc6842#page-4 */
 		if (ret->options[DHCP_OPT_CLASS_ID].len != client->self_id_len ||
-		    memcmp(ret->options[DHCP_OPT_CLASS_ID].dat, client->self_id_dat, client->self_id_len))
+		    memcmp(&ret->option_dat[ret->options[DHCP_OPT_CLASS_ID].off], client->self_id_dat, client->self_id_len))
 			/* ignore messages that aren't to us */
 			goto ignore;
 	}
@@ -704,23 +704,23 @@ static void dhcp_client_take_lease(struct dhcp_client *client, struct dhcp_recv_
 
 	client->lease_client_addr = msg->raw.yiaddr;
 	client->lease_auxdata.subnet_mask = msg->options[DHCP_OPT_SUBNET_MASK].len
-		? *((struct net_ip4_addr *)msg->options[DHCP_OPT_SUBNET_MASK].dat)
+		? *((struct net_ip4_addr *)&msg->option_dat[msg->options[DHCP_OPT_SUBNET_MASK].off])
 		: net_ip4_addr_zero;
 	client->lease_auxdata.gateway_addr = msg->options[DHCP_OPT_ROUTER].len
-		? *((struct net_ip4_addr *)msg->options[DHCP_OPT_SUBNET_MASK].dat)
+		? *((struct net_ip4_addr *)&msg->option_dat[msg->options[DHCP_OPT_SUBNET_MASK].off])
 		: net_ip4_addr_zero;
 	client->lease_server_id   =
-		*((struct net_ip4_addr *)msg->options[DHCP_OPT_DHCP_SERVER_ID].dat);
+		*((struct net_ip4_addr *)&msg->option_dat[msg->options[DHCP_OPT_DHCP_SERVER_ID].off]);
 
 	uint64_t dur_ns_end =
-		((uint64_t)uint32be_decode(msg->options[DHCP_OPT_ADDRESS_TIME].dat))*NS_PER_S;
+		((uint64_t)uint32be_decode(&msg->option_dat[msg->options[DHCP_OPT_ADDRESS_TIME].off]))*NS_PER_S;
 	uint64_t dur_ns_t1 = msg->options[DHCP_OPT_RENEWAL_TIME].len
-		? ((uint64_t)uint32be_decode(msg->options[DHCP_OPT_RENEWAL_TIME].dat))*NS_PER_S
+		? ((uint64_t)uint32be_decode(&msg->option_dat[msg->options[DHCP_OPT_RENEWAL_TIME].off]))*NS_PER_S
 		: (dur_ns_end == DHCP_INFINITY * NS_PER_S)
 		  ? DHCP_INFINITY * NS_PER_S
 		  : dur_ns_end/2;
 	uint64_t dur_ns_t2 =  msg->options[DHCP_OPT_REBINDING_TIME].len
-		? ((uint64_t)uint32be_decode(msg->options[DHCP_OPT_RENEWAL_TIME].dat))*NS_PER_S
+		? ((uint64_t)uint32be_decode(&msg->option_dat[msg->options[DHCP_OPT_RENEWAL_TIME].off]))*NS_PER_S
 		: (dur_ns_end == DHCP_INFINITY * NS_PER_S)
 		  ? DHCP_INFINITY * NS_PER_S
 		  : (dur_ns_end*7)/8; /* 0.875 = 7/8 */
@@ -762,7 +762,7 @@ static __attribute__((noreturn)) void dhcp_client_run(struct dhcp_client *client
 			VCALL(client->sock, set_read_deadline, client->time_ns_init+CONFIG_DHCP_SELECTING_NS);
 			switch ((r = dhcp_client_recv(client, scratch_msg))) {
 			case 0:
-				switch (scratch_msg->options[DHCP_OPT_DHCP_MSG_TYPE].dat[0]) {
+				switch (scratch_msg->option_dat[scratch_msg->options[DHCP_OPT_DHCP_MSG_TYPE].off]) {
 				case DHCP_MSGTYP_OFFER:
 					/* Accept the first offer.  */
 					dhcp_client_take_lease(client, scratch_msg, false);
@@ -784,7 +784,7 @@ static __attribute__((noreturn)) void dhcp_client_run(struct dhcp_client *client
 			VCALL(client->sock, set_read_deadline, 0);
 			switch ((r = dhcp_client_recv(client, scratch_msg))) {
 			case 0:
-				switch (scratch_msg->options[DHCP_OPT_DHCP_MSG_TYPE].dat[0]) {
+				switch (scratch_msg->option_dat[scratch_msg->options[DHCP_OPT_DHCP_MSG_TYPE].off]) {
 				case DHCP_MSGTYP_NAK:
 					dhcp_client_setstate(client, STATE_INIT, 0, NULL, scratch_msg);
 					break;
@@ -826,7 +826,7 @@ static __attribute__((noreturn)) void dhcp_client_run(struct dhcp_client *client
 			VCALL(client->sock, set_read_deadline, client->lease_time_ns_t2);
 			switch ((r = dhcp_client_recv(client, scratch_msg))) {
 			case 0:
-				switch (scratch_msg->options[DHCP_OPT_DHCP_MSG_TYPE].dat[0]) {
+				switch (scratch_msg->option_dat[scratch_msg->options[DHCP_OPT_DHCP_MSG_TYPE].off]) {
 				case DHCP_MSGTYP_NAK:
 					VCALL(client->iface, ifdown);
 					dhcp_client_setstate(client, STATE_INIT, 0, NULL, scratch_msg);
@@ -852,7 +852,7 @@ static __attribute__((noreturn)) void dhcp_client_run(struct dhcp_client *client
 			VCALL(client->sock, set_read_deadline, client->lease_time_ns_end);
 			switch ((r = dhcp_client_recv(client, scratch_msg))) {
 			case 0:
-				switch (scratch_msg->options[DHCP_OPT_DHCP_MSG_TYPE].dat[0]) {
+				switch (scratch_msg->option_dat[scratch_msg->options[DHCP_OPT_DHCP_MSG_TYPE].off]) {
 				case DHCP_MSGTYP_NAK:
 					VCALL(client->iface, ifdown);
 					dhcp_client_setstate(client, STATE_BOUND, 0, NULL, scratch_msg);