add library to override addresses

build/files/addr_aliases.c

@@ -0,0 +1,44 @@
+#include <resolv.h>
+#include <netdb.h>
+
+#define __USE_GNU
+#include <dlfcn.h>
+
+#include <stdio.h>
+#include <string.h>
+#include <stdlib.h>
+
+const char* getfield(char* line, int num) {
+    char* tmp = strdup(line);
+    const char* tok;
+    for (tok = strtok(tmp, " "); 
+         tok && *tok;
+         tok = strtok(NULL, " ")) {
+        if (--num < 0) {
+            return strdup(tok);
+        }
+    }
+    return NULL;
+}
+
+int getaddrinfo(const char *node, const char *service, const struct addrinfo *hints, struct addrinfo **res) {
+    FILE* stream = fopen("/host/etc/addr_aliases", "r");
+    char line[1024];
+    while (fgets(line, 1024, stream)) {        
+        const char* host_from = getfield(line, 0);
+        const char* port_from = getfield(line, 1);
+        const char* host_to = getfield(line, 2);
+        const char* port_to = getfield(line, 3);
+        if (strcmp(node, host_from) == 0 && strcmp(service, port_from) == 0) {
+            fprintf(stderr, "%s:%s => %s:%s\n", host_from, port_from, host_to, port_to);
+            node = host_to;
+            service = host_to;
+        }
+    }
+	if (res_init () < 0) {
+		return EAI_SYSTEM;
+    } else {
+        int (*f)() = dlsym (RTLD_NEXT, "getaddrinfo");
+        return f(node, service, hints, res);
+    }
+}