From 8f89f98254f5bd3036cd72394210ce9aa2bc845f Mon Sep 17 00:00:00 2001
From: calesanz <8714917+calesanz@users.noreply.github.com>
Date: Tue, 8 Feb 2022 20:59:17 +0100
Subject: [PATCH] Add generic way to retreive libc path

---
 daemon/dns/ebpfhook.go | 63 ++++++++++++++++++++++++++++++++++++++++--
 1 file changed, 61 insertions(+), 2 deletions(-)

diff --git a/daemon/dns/ebpfhook.go b/daemon/dns/ebpfhook.go
index 8c6f9be06f..776488fbb1 100644
--- a/daemon/dns/ebpfhook.go
+++ b/daemon/dns/ebpfhook.go
@@ -15,7 +15,49 @@ import (
 	bpf "github.com/iovisor/gobpf/elf"
 )
 
-var libcFile = "/lib/libc.so.6"
+/*
+#cgo LDFLAGS: -ldl
+
+#define _GNU_SOURCE
+#include <stdio.h>
+#include <stdlib.h>
+#include <link.h>
+#include <dlfcn.h>
+#include <string.h>
+
+char* find_libc() {
+    void *handle;
+    struct link_map * map;
+
+    handle = dlopen(NULL, RTLD_NOW);
+    if (handle == NULL) {
+        fprintf(stderr, "EBPF-DNS dlopen() failed: %s\n", dlerror());
+        return NULL;
+    }
+
+
+    if (dlinfo(handle, RTLD_DI_LINKMAP, &map) == -1) {
+        fprintf(stderr, "EBPF-DNS: dlinfo failed: %s\n", dlerror());
+        return NULL;
+    }
+
+    while(1){
+        if(map == NULL){
+            break;
+        }
+
+        if(strstr(map->l_name, "libc.so")){
+            fprintf(stderr,"found %s\n", map->l_name);
+            return map->l_name;
+        }
+        map = map->l_next;
+    }
+    return NULL;
+}
+
+
+*/
+import "C"
 
 type nameLookupEvent struct {
 	AddrType uint32
@@ -23,6 +65,17 @@ type nameLookupEvent struct {
 	Host     [252]byte
 }
 
+func findLibc() (string, error) {
+	ret := C.find_libc()
+
+	if ret == nil {
+		return "", errors.New("Could not find path to libc.so")
+	}
+	str := C.GoString(ret)
+
+	return str, nil
+}
+
 // Iterates over all symbols in an elf file and returns the offset matching the provided symbol name.
 func lookupSymbol(elffile *elf.File, symbolName string) (uint64, error) {
 	symbols, err := elffile.Symbols()
@@ -50,10 +103,16 @@ func DnsListenerEbpf() error {
 	// some how 0 must be replaced with the offset of getaddrinfo bcc does this using bcc_resolve_symname
 
 	// Attaching to uprobe using perf open might be a better aproach requires https://github.com/iovisor/gobpf/pull/277
+	libcFile, err := findLibc()
+
+	if err != nil {
+		log.Error("EBPF-DNS: Failed to find libc.so: %v", err)
+		return err
+	}
 
 	libc_elf, err := elf.Open(libcFile)
 	if err != nil {
-		log.Error("EBPF-DNS: Failed to find libc.so.6: %v", err)
+		log.Error("EBPF-DNS: Failed to open %s: %v", libcFile, err)
 		return err
 	}