providing sock from main thread in order to faciliate dropping privs

src/send.c

@@ -132,7 +132,7 @@ int send_init(void)
 	return EXIT_SUCCESS;
 }
 
-static int get_socket(void)
+int get_socket(void)
 {
 	int sock = socket(AF_PACKET, SOCK_RAW, htons(ETH_P_ALL));
 	if (sock <= 0) {
@@ -142,7 +142,7 @@ static int get_socket(void)
 	return sock;
 }
 
-static int get_dryrun_socket(void)
+int get_dryrun_socket(void)
 {
 	// we need a socket in order to gather details about the system
 	// such as source MAC address and IP address. However, because
@@ -167,16 +167,11 @@ static inline ipaddr_n_t get_src_ip(ipaddr_n_t dst, int local_offset)
 }
 
 // one sender thread
-int send_run(void)
+int send_run(int sock)
 {
 	log_debug("send", "thread started");
 	pthread_mutex_lock(&send_mutex);
-	int sock;
-	if (zconf.dryrun) {
-		sock = get_dryrun_socket();
-	} else {
-		sock = get_socket();
-	}
+	
 	struct sockaddr_ll sockaddr;
 	// get source interface index
 	struct ifreq if_idx;

src/send.h

@@ -9,7 +9,9 @@
 #ifndef SEND_H
 #define SEND_H
 
+int get_socket(void);
+int get_dryrun_socket(void);
 int send_init(void);
-int send_run(void);
+int send_run(int);
 
-#endif //_SEND_H
+#endif //SEND_H

src/zmap.c

@@ -90,10 +90,12 @@ static void set_cpu(void)
 	pthread_mutex_unlock(&cpu_affinity_mutex);
 }	
 
-static void* start_send(__attribute__((unused)) void *arg)
+static void* start_send(void *arg)
 {
+	uintptr_t v = (uintptr_t) arg;
+	int sock = (int) v & 0xFFFF;
 	set_cpu();
-	send_run();
+	send_run(sock);
 	return NULL;
 }
 
@@ -238,7 +240,14 @@ static void start_zmap(void)
 	assert(tsend);
 	log_debug("zmap", "using %d sender threads", zconf.senders);
 	for (int i=0; i < zconf.senders; i++) {
-		int r = pthread_create(&tsend[i], NULL, start_send, NULL);
+	uintptr_t sock;
+		if (zconf.dryrun) {
+			sock = get_dryrun_socket();
+		} else {
+			sock = get_socket();
+		}
+		
+		int r = pthread_create(&tsend[i], NULL, start_send, (void*) sock);
 		if (r != 0) {
 			log_fatal("zmap", "unable to create send thread");
 			exit(EXIT_FAILURE);