Use specific outbound IP address

Fixes #14

Signed-off-by: 5eraph <bcervenka@protonmail.com>

8 files changed, 58 insertions, 1 deletions

diff --git a/src/ip_icmp.c b/src/ip_icmp.c
index 58e35a5..fe0add4 100644
--- a/src/ip_icmp.c
+++ b/src/ip_icmp.c
@@ -90,6 +90,13 @@ static int icmp_send(struct socket *so, struct mbuf *m, int hlen)
         return -1;
     }
 
+    if (slirp_bind_outbound(so, AF_INET) != 0) {
+        // bind failed - close socket
+        closesocket(so->s);
+        so->s = -1;
+        return -1;
+    }
+
     so->so_m = m;
     so->so_faddr = ip->ip_dst;
     so->so_laddr = ip->ip_src;
diff --git a/src/libslirp.h b/src/libslirp.h
index ad93edf..fb4c7e8 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 1
+#define SLIRP_CONFIG_VERSION_MAX 2
 
 typedef struct SlirpConfig {
     /* Version must be provided */
@@ -107,6 +107,8 @@ typedef struct SlirpConfig {
     /*
      * Fields introduced in SlirpConfig version 2 begin
      */
+    struct sockaddr_in *outbound_addr;
+    struct sockaddr_in6 *outbound_addr6;
 } SlirpConfig;
 
 Slirp *slirp_new(const SlirpConfig *cfg, const SlirpCb *callbacks,
diff --git a/src/misc.c b/src/misc.c
index ddbe43d..e6bc0a2 100644
--- a/src/misc.c
+++ b/src/misc.c
@@ -368,3 +368,23 @@ char *slirp_connection_info(Slirp *slirp)
 
     return g_string_free(str, FALSE);
 }
+
+int slirp_bind_outbound(struct socket *so, unsigned short af)
+{
+    int ret = 0;
+    struct sockaddr *addr = NULL;
+    int addr_size = 0;
+
+    if (af == AF_INET && so->slirp->outbound_addr != NULL) {
+        addr = (struct sockaddr *)so->slirp->outbound_addr;
+        addr_size = sizeof(struct sockaddr_in);
+    } else if (af == AF_INET6 && so->slirp->outbound_addr6 != NULL) {
+        addr = (struct sockaddr *)so->slirp->outbound_addr6;
+        addr_size = sizeof(struct sockaddr_in6);
+    }
+
+    if (addr != NULL) {
+        ret = bind(so->s, addr, addr_size);
+    }
+    return ret;
+}
\ No newline at end of file
diff --git a/src/misc.h b/src/misc.h
index 841b0a7..81b370c 100644
--- a/src/misc.h
+++ b/src/misc.h
@@ -67,4 +67,6 @@ struct gfwd_list *add_unix(struct gfwd_list **ex_ptr, const char *unixsock,
 
 int remove_guestfwd(struct gfwd_list **ex_ptr, struct in_addr addr, int port);
 
+int slirp_bind_outbound(struct socket *so, unsigned short af);
+
 #endif
diff --git a/src/slirp.c b/src/slirp.c
index e0b53a7..4967475 100644
--- a/src/slirp.c
+++ b/src/slirp.c
@@ -326,6 +326,13 @@ Slirp *slirp_new(const SlirpConfig *cfg, const SlirpCb *callbacks, void *opaque)
     slirp->disable_host_loopback = cfg->disable_host_loopback;
     slirp->enable_emu = cfg->enable_emu;
 
+    if (cfg->version >= 2) {
+        slirp->outbound_addr = cfg->outbound_addr;
+        slirp->outbound_addr6 = cfg->outbound_addr6;
+    } else {
+        slirp->outbound_addr = NULL;
+        slirp->outbound_addr6 = NULL;
+    }
     return slirp;
 }
 
diff --git a/src/slirp.h b/src/slirp.h
index a231eb2..32634bc 100644
--- a/src/slirp.h
+++ b/src/slirp.h
@@ -199,6 +199,9 @@ struct Slirp {
 
     const SlirpCb *cb;
     void *opaque;
+
+    struct sockaddr_in *outbound_addr;
+    struct sockaddr_in6 *outbound_addr6;
 };
 
 void if_start(Slirp *);
diff --git a/src/tcp_subr.c b/src/tcp_subr.c
index 9dc541a..a1016d9 100644
--- a/src/tcp_subr.c
+++ b/src/tcp_subr.c
@@ -407,6 +407,16 @@ int tcp_fconnect(struct socket *so, unsigned short af)
 
     ret = so->s = slirp_socket(af, SOCK_STREAM, 0);
     if (ret >= 0) {
+        ret = slirp_bind_outbound(so, af);
+        if (ret < 0) {
+            // bind failed - close socket
+            closesocket(so->s);
+            so->s = -1;
+            return (ret);
+        }
+    }
+
+    if (ret >= 0) {
         int opt, s = so->s;
         struct sockaddr_storage addr;
 
diff --git a/src/udp.c b/src/udp.c
index 35218a9..6bde20f 100644
--- a/src/udp.c
+++ b/src/udp.c
@@ -279,6 +279,12 @@ int udp_attach(struct socket *so, unsigned short af)
 {
     so->s = slirp_socket(af, SOCK_DGRAM, 0);
     if (so->s != -1) {
+        if (slirp_bind_outbound(so, af) != 0) {
+            // bind failed - close socket
+            closesocket(so->s);
+            so->s = -1;
+            return -1;
+        }
         so->so_expire = curtime + SO_EXPIRE;
         insque(so, &so->slirp->udb);
     }