slirp: Enable multiple instances

Once again this was a long journey to reach the destination: Allow to instantiate slirp multiple times. But as in the past, the journey was worthwhile, cleaning up, fixing and enhancing various parts of the user space network stack along the way. What is this particular change good for? Multiple slirps instances allow separated user space networks for guests with multiple NICs. This is already possible, but without any slirp support for the second network, ie. without a chance to talk to that network from the host via IP. We have a legacy guest system here that benefits from this slirp enhancement, allowing us to run both of its NICs purely over unprivileged user space IP stacks. Another benefit of this patch is that it simply removes an artificial restriction of the configuration space qemu is providing, avoiding another source of surprises that users may face when playing with possible setups. Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com> Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>

slirp: Enable multiple instances
Once again this was a long journey to reach the destination: Allow to instantiate slirp multiple times. But as in the past, the journey was worthwhile, cleaning up, fixing and enhancing various parts of the user space network stack along the way. What is this particular change good for? Multiple slirps instances allow separated user space networks for guests with multiple NICs. This is already possible, but without any slirp support for the second network, ie. without a chance to talk to that network from the host via IP. We have a legacy guest system here that benefits from this slirp enhancement, allowing us to run both of its NICs purely over unprivileged user space IP stacks. Another benefit of this patch is that it simply removes an artificial restriction of the configuration space qemu is providing, avoiding another source of surprises that users may face when playing with possible setups. Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com> Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
Jan Kiszka · Anthony Liguori
1 parent ad0d8c4c
Showing 3 changed files with 37 additions and 27 deletions
net.c
slirp/slirp.c
slirp/slirp.h
@@ -678,6 +678,7 @@ struct slirp_config_str {
 };
 typedef struct SlirpState {
+    TAILQ_ENTRY(SlirpState) entry;
     VLANClientState *vc;
     Slirp *slirp;
 } SlirpState;
@@ -685,7 +686,8 @@ typedef struct SlirpState {
 static struct slirp_config_str *slirp_configs;
 const char *legacy_tftp_prefix;
 const char *legacy_bootp_filename;
-static SlirpState *slirp_state;
+static TAILQ_HEAD(slirp_stacks, SlirpState) slirp_stacks =
+    TAILQ_HEAD_INITIALIZER(slirp_stacks);
 static void slirp_hostfwd(SlirpState *s, Monitor *mon, const char *redir_str,
                           int legacy_format);
@@ -734,7 +736,7 @@ static void net_slirp_cleanup(VLANClientState *vc)
     SlirpState *s = vc->opaque;
     slirp_cleanup(s->slirp);
-    slirp_state = NULL;
+    TAILQ_REMOVE(&slirp_stacks, s, entry);
     qemu_free(s);
 }
@@ -842,7 +844,7 @@ static int net_slirp_init(Monitor *mon, VLANState *vlan, const char *model,
     s = qemu_mallocz(sizeof(SlirpState));
     s->slirp = slirp_init(restricted, net, mask, host, vhostname,
                           tftp_export, bootfile, dhcp, dns, s);
-    slirp_state = s;
+    TAILQ_INSERT_TAIL(&slirp_stacks, s, entry);
     while (slirp_configs) {
         struct slirp_config_str *config = slirp_configs;
@@ -881,7 +883,7 @@ void net_slirp_hostfwd_remove(Monitor *mon, const char *src_str)
     int is_udp = 0;
     int err;
-    if (!slirp_state) {
+    if (TAILQ_EMPTY(&slirp_stacks)) {
         monitor_printf(mon, "user mode network stack not in use\n");
         return;
     }
@@ -908,7 +910,7 @@ void net_slirp_hostfwd_remove(Monitor *mon, const char *src_str)
     host_port = atoi(p);
-    err = slirp_remove_hostfwd(slirp_state->slirp, is_udp,
+    err = slirp_remove_hostfwd(TAILQ_FIRST(&slirp_stacks)->slirp, is_udp,
                                host_addr, host_port);
     monitor_printf(mon, "host forwarding rule for %s %s\n", src_str,
@@ -984,19 +986,19 @@ static void slirp_hostfwd(SlirpState *s, Monitor *mon, const char *redir_str,
 void net_slirp_hostfwd_add(Monitor *mon, const char *redir_str)
 {
-    if (!slirp_state) {
+    if (TAILQ_EMPTY(&slirp_stacks)) {
         monitor_printf(mon, "user mode network stack not in use\n");
         return;
     }
-    slirp_hostfwd(slirp_state, mon, redir_str, 0);
+    slirp_hostfwd(TAILQ_FIRST(&slirp_stacks), mon, redir_str, 0);
 }
 void net_slirp_redir(const char *redir_str)
 {
     struct slirp_config_str *config;
-    if (!slirp_state) {
+    if (TAILQ_EMPTY(&slirp_stacks)) {
         config = qemu_malloc(sizeof(*config));
         pstrcpy(config->str, sizeof(config->str), redir_str);
         config->flags = SLIRP_CFG_HOSTFWD | SLIRP_CFG_LEGACY;
@@ -1005,7 +1007,7 @@ void net_slirp_redir(const char *redir_str)
         return;
     }
-    slirp_hostfwd(slirp_state, NULL, redir_str, 1);
+    slirp_hostfwd(TAILQ_FIRST(&slirp_stacks), NULL, redir_str, 1);
 }
 #ifndef _WIN32
@@ -1106,8 +1108,8 @@ void net_slirp_smb(const char *exported_dir)
         exit(1);
     }
     legacy_smb_export = exported_dir;
-    if (slirp_state) {
-        slirp_smb(slirp_state, exported_dir, vserver_addr);
+    if (!TAILQ_EMPTY(&slirp_stacks)) {
+        slirp_smb(TAILQ_FIRST(&slirp_stacks), exported_dir, vserver_addr);
     }
 }
@@ -1198,13 +1200,12 @@ static void slirp_guestfwd(SlirpState *s, Monitor *mon, const char *config_str,
 void do_info_usernet(Monitor *mon)
 {
-    SlirpState *s = slirp_state;
+    SlirpState *s;
-    if (!s) {
-        return;
+    TAILQ_FOREACH(s, &slirp_stacks, entry) {
+        monitor_printf(mon, "VLAN %d (%s):\n", s->vc->vlan->id, s->vc->name);
+        slirp_connection_info(s->slirp, mon);
     }
-    monitor_printf(mon, "VLAN %d (%s):\n", s->vc->vlan->id, s->vc->name);
-    slirp_connection_info(s->slirp, mon);
 }
 #endif /* CONFIG_SLIRP */
@@ -2515,7 +2516,7 @@ int net_client_init(Monitor *mon, const char *device, const char *p)
         qemu_free(smb_export);
         qemu_free(vsmbsrv);
     } else if (!strcmp(device, "channel")) {
-        if (!slirp_state) {
+        if (TAILQ_EMPTY(&slirp_stacks)) {
             struct slirp_config_str *config;
             config = qemu_malloc(sizeof(*config));
@@ -2524,7 +2525,7 @@ int net_client_init(Monitor *mon, const char *device, const char *p)
             config->next = slirp_configs;
             slirp_configs = config;
         } else {
-            slirp_guestfwd(slirp_state, mon, p, 1);
+            slirp_guestfwd(TAILQ_FIRST(&slirp_stacks), mon, p, 1);
         }
         ret = 0;
     } else
@@ -47,7 +47,8 @@ u_int curtime;
 static u_int time_fasttimo, last_slowtimo;
 static int do_slowtimo;
-Slirp *slirp_instance;
+TAILQ_HEAD(slirp_instances, Slirp) slirp_instances =
+    TAILQ_HEAD_INITIALIZER(slirp_instances);
 #ifdef _WIN32
@@ -223,20 +224,20 @@ Slirp *slirp_init(int restricted, struct in_addr vnetwork,
     register_savevm("slirp", 0, 2, slirp_state_save, slirp_state_load, slirp);
-    slirp_instance = slirp;
+    TAILQ_INSERT_TAIL(&slirp_instances, slirp, entry);
     return slirp;
 }
 void slirp_cleanup(Slirp *slirp)
 {
+    TAILQ_REMOVE(&slirp_instances, slirp, entry);
+
     unregister_savevm("slirp", slirp);
     qemu_free(slirp->tftp_prefix);
     qemu_free(slirp->bootp_filename);
     qemu_free(slirp);
-
-    slirp_instance = NULL;
 }
 #define CONN_CANFSEND(so) (((so)->so_state & (SS_FCANTSENDMORE|SS_ISFCONNECTED)) == SS_ISFCONNECTED)
@@ -269,11 +270,11 @@ static void updtime(void)
 void slirp_select_fill(int *pnfds,
                        fd_set *readfds, fd_set *writefds, fd_set *xfds)
 {
-    Slirp *slirp = slirp_instance;
+    Slirp *slirp;
     struct socket *so, *so_next;
     int nfds;
-    if (!slirp_instance) {
+    if (TAILQ_EMPTY(&slirp_instances)) {
         return;
     }
@@ -288,11 +289,12 @@ void slirp_select_fill(int *pnfds,
 	 */
 	do_slowtimo = 0;
+	TAILQ_FOREACH(slirp, &slirp_instances, entry) {
 		/*
 		 * *_slowtimo needs calling if there are IP fragments
 		 * in the fragment queue, or there are TCP connections active
 		 */
-		do_slowtimo = ((slirp->tcb.so_next != &slirp->tcb) ||
+		do_slowtimo |= ((slirp->tcb.so_next != &slirp->tcb) ||
 		    (&slirp->ipq.ip_link != slirp->ipq.ip_link.next));
 		for (so = slirp->tcb.so_next; so != &slirp->tcb;
@@ -383,6 +385,7 @@ void slirp_select_fill(int *pnfds,
 				UPD_NFDS(so->s);
 			}
 		}
+	}
         *pnfds = nfds;
 }
@@ -390,11 +393,11 @@ void slirp_select_fill(int *pnfds,
 void slirp_select_poll(fd_set *readfds, fd_set *writefds, fd_set *xfds,
                        int select_error)
 {
-    Slirp *slirp = slirp_instance;
+    Slirp *slirp;
     struct socket *so, *so_next;
     int ret;
-    if (!slirp_instance) {
+    if (TAILQ_EMPTY(&slirp_instances)) {
         return;
     }
@@ -405,6 +408,7 @@ void slirp_select_poll(fd_set *readfds, fd_set *writefds, fd_set *xfds,
 	/* Update time */
 	updtime();
+    TAILQ_FOREACH(slirp, &slirp_instances, entry) {
 	/*
 	 * See if anything has timed out
 	 */
@@ -559,6 +563,7 @@ void slirp_select_poll(fd_set *readfds, fd_set *writefds, fd_set *xfds,
 	if (slirp->if_queued) {
 	    if_start(slirp);
 	}
+    }
 	/* clear global file descriptor sets.
 	 * these reside on the stack in vl.c
@@ -185,6 +185,8 @@ int inet_aton _P((const char *cp, struct in_addr *ia));
 #include "debug.h"
+#include "sys-queue.h"
+
 #include "libslirp.h"
 #include "ip.h"
 #include "tcp.h"
@@ -207,6 +209,8 @@ int inet_aton _P((const char *cp, struct in_addr *ia));
 #include "tftp.h"
 struct Slirp {
+    TAILQ_ENTRY(Slirp) entry;
+
     /* virtual network configuration */
     struct in_addr vnetwork_addr;
     struct in_addr vnetwork_mask;