Merge branch 'master' into 'master'

Limit dns passthrough to port 53 only and `disable_dns`

Closes #16

See merge request slirp/libslirp!31

4 files changed, 14 insertions, 5 deletions

diff --git a/src/libslirp.h b/src/libslirp.h
index fb4c7e8..caea7ed 100644
--- a/src/libslirp.h
+++ b/src/libslirp.h
@@ -67,7 +67,7 @@ typedef struct SlirpCb {
 } SlirpCb;
 
 #define SLIRP_CONFIG_VERSION_MIN 1
-#define SLIRP_CONFIG_VERSION_MAX 2
+#define SLIRP_CONFIG_VERSION_MAX 3
 
 typedef struct SlirpConfig {
     /* Version must be provided */
@@ -109,6 +109,7 @@ typedef struct SlirpConfig {
      */
     struct sockaddr_in *outbound_addr;
     struct sockaddr_in6 *outbound_addr6;
+    bool disable_dns;  /* slirp will not redirect/serve any DNS packet */
 } SlirpConfig;
 
 Slirp *slirp_new(const SlirpConfig *cfg, const SlirpCb *callbacks,
diff --git a/src/slirp.c b/src/slirp.c
index 14458e8..4053d34 100644
--- a/src/slirp.c
+++ b/src/slirp.c
@@ -338,6 +338,13 @@ Slirp *slirp_new(const SlirpConfig *cfg, const SlirpCb *callbacks, void *opaque)
         slirp->outbound_addr = NULL;
         slirp->outbound_addr6 = NULL;
     }
+
+    if (cfg->version >= 3) {
+        slirp->disable_dns = cfg->disable_dns;
+    } else {
+        slirp->disable_dns = false;
+    }
+
     return slirp;
 }
 
diff --git a/src/slirp.h b/src/slirp.h
index 32634bc..47d861b 100644
--- a/src/slirp.h
+++ b/src/slirp.h
@@ -202,6 +202,7 @@ struct Slirp {
 
     struct sockaddr_in *outbound_addr;
     struct sockaddr_in6 *outbound_addr6;
+    bool disable_dns; /* slirp will not redirect/serve any DNS packet */
 };
 
 void if_start(Slirp *);
diff --git a/src/socket.c b/src/socket.c
index 4cd9a64..cd2f89e 100644
--- a/src/socket.c
+++ b/src/socket.c
@@ -821,8 +821,8 @@ void sofwdrain(struct socket *so)
 
 static bool sotranslate_out4(Slirp *s, struct socket *so, struct sockaddr_in *sin)
 {
-    if (so->so_faddr.s_addr == s->vnameserver_addr.s_addr) {
-        return get_dns_addr(&sin->sin_addr) >= 0;
+    if (!s->disable_dns && so->so_faddr.s_addr == s->vnameserver_addr.s_addr) {
+        return so->so_fport == htons(53) && get_dns_addr(&sin->sin_addr) >= 0;
     }
 
     if (so->so_faddr.s_addr == s->vhost_addr.s_addr ||
@@ -839,9 +839,9 @@ static bool sotranslate_out4(Slirp *s, struct socket *so, struct sockaddr_in *si
 
 static bool sotranslate_out6(Slirp *s, struct socket *so, struct sockaddr_in6 *sin)
 {
-    if (in6_equal(&so->so_faddr6, &s->vnameserver_addr6)) {
+    if (!s->disable_dns && in6_equal(&so->so_faddr6, &s->vnameserver_addr6)) {
         uint32_t scope_id;
-        if (get_dns6_addr(&sin->sin6_addr, &scope_id) >= 0) {
+        if (so->so_fport == htons(53) && get_dns6_addr(&sin->sin6_addr, &scope_id) >= 0) {
             sin->sin6_scope_id = scope_id;
             return true;
         }