X-Git-Url: http://www.chiark.greenend.org.uk/ucgi/~ianmdlvl/git?p=secnet.git;a=blobdiff_plain;f=polypath.c;h=0f68a496d54ee6744b8558620472f5a16b5c72fa;hp=3bd835e12759c9f7ddc74878e6e2ea1e0e548463;hb=2d80199d7bc25b4c6e4a5ac986f8902770e82d96;hpb=e61a41a48cdc15d9743731deed717961fdcf4da2

diff --git a/polypath.c b/polypath.c
index 3bd835e..0f68a49 100644
--- a/polypath.c
+++ b/polypath.c
@@ -1,6 +1,24 @@
 /* polypath
  * send/receive module for secnet
  * for multi-route setups */
+/*
+ * This file is part of secnet.
+ * See README for full list of copyright holders.
+ *
+ * secnet is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version d of the License, or
+ * (at your option) any later version.
+ * 
+ * secnet is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ * 
+ * You should have received a copy of the GNU General Public License
+ * version 3 along with secnet; if not, see
+ * https://www.gnu.org/licenses/gpl.html.
+ */
 
 #include "secnet.h"
 #include "util.h"
@@ -31,8 +49,12 @@ struct polypath {
     struct buffer_if lbuf;
     int monitor_fd;
     pid_t monitor_pid;
+    int privsep_incoming_fd;
+    int privsep_ipcsock_fd;
 };
 
+static void polypath_phase_shutdown(void *sst, uint32_t newphase);
+
 #define LG 0, st->uc.cc.cl.description, &st->uc.cc.loc
 
 static const char *const default_loopback_ifname_pats[] = {
@@ -108,36 +130,6 @@ static int polypath_beforepoll(void *state, struct pollfd *fds, int *nfds_io,
     return 0;
 }
 
-static void dump_ppml(struct polypath *st, const char *orgl)
-{
-#ifdef POLYPATH_DEBUG
-    struct interf *interf;
-    if (orgl)
-	lg_perror(LG,M_DEBUG,0, "polypath monitor line `%s'",orgl);
-    LIST_FOREACH(interf, &st->interfs, entry) {
-	lg_perror(LG,M_DEBUG,0, "  polypath interface `%s', nsocks=%d",
-		  interf->name, interf->socks.n_socks);
-	int i;
-	for (i=0; i<interf->socks.n_socks; i++) {
-	    struct udpsock *us=&interf->socks.socks[i];
-	    lg_perror(LG,M_DEBUG,0, "    polypath sock fd=%d addr=%s",
-		      us->fd, iaddr_to_string(&us->addr));
-	}
-    }
-#endif
-}
-
-static void bad(struct polypath *st, char *l, char *undospace,
-		const char *m, int ev)
-{
-    if (undospace)
-	*undospace=' ';
-    lg_perror(LG,M_WARNING,ev,
-	       "error processing polypath state change: %s"
-	       " (while processing `%s')",
-	       m,l);
-}
-
 static inline bool_t matches32(uint32_t word, uint32_t prefix, int prefixlen)
 {
     assert(prefixlen>0);
@@ -147,18 +139,50 @@ static inline bool_t matches32(uint32_t word, uint32_t prefix, int prefixlen)
     return (word & mask) == prefix;
 }
 
-static void polypath_process_monitor_line(struct polypath *st, char *orgl)
+/* These macros expect
+ *    bad_fn_type *const bad;
+ *    void *badctx;
+ * and
+ *   out:
+ */
+#define BAD(m)     do{ bad(st,badctx,M_WARNING,m,0);  goto out; }while(0)
+#define BADE(m,ev) do{ bad(st,badctx,M_WARNING,m,ev); goto out; }while(0)
+typedef void bad_fn_type(struct polypath *st, void *badctx,
+			 int mclass, const char* m, int ev);
+
+typedef void polypath_ppml_callback_type(struct polypath *st,
+          bad_fn_type *bad, void *badctx,
+          bool_t add, const char *ifname, const char *ifaddr,
+          const union iaddr *ia, int fd /* -1 if none yet */);
+
+struct ppml_bad_ctx {
+    const char *orgl;
+    char *undospace;
+};
+
+static void ppml_bad(struct polypath *st, void *badctx,
+		     int mclass, const char *m, int ev)
+{
+    struct ppml_bad_ctx *bc=badctx;
+    if (bc->undospace)
+	*(bc->undospace)=' ';
+    lg_perror(LG,mclass,ev,
+	      "error processing polypath state change: %s"
+	      " (while processing `%s')",
+	      m,bc->orgl);
+}
+
+static void polypath_process_monitor_line(struct polypath *st, char *orgl,
+                                      polypath_ppml_callback_type *callback)
+    /* always calls callback with fd==-1 */
 {
-    struct interf *interf=0;
     struct udpcommon *uc=&st->uc;
-    char *undospace=0;
     char *l=orgl;
-    struct udpsock *us=0;
-
-    dump_ppml(st,orgl);
-
-#define BAD(m)     do{ bad(st,orgl,undospace,m,0);  goto out; }while(0)
-#define BADE(m,ev) do{ bad(st,orgl,undospace,m,ev); goto out; }while(0)
+    bad_fn_type (*const bad)=ppml_bad;
+    struct ppml_bad_ctx badctx[1]={{
+	    .orgl=orgl,
+	    .undospace=0
+	}};
 
     bool_t add;
     int c=*l++;
@@ -180,7 +204,7 @@ static void polypath_process_monitor_line(struct polypath *st, char *orgl)
     if (!space) BAD("no second space");
     const char *ifaddr=space+1;
     *space=0;
-    undospace=space;
+    badctx->undospace=space;
 
     union iaddr ia;
     FILLZERO(ia);
@@ -220,6 +244,7 @@ static void polypath_process_monitor_line(struct polypath *st, char *orgl)
 	    DONT("IPv6 address is " m)
         DONTMASK( 100,   0,  8, "Discard-Only (RFC6666)");
 	DONTMASK(2001,   0, 23, "in IETF protocol block (RFC2928)");
+	DONTMASK(fc00,   0,  7, "Uniqe Local unicast (RFC4193)");
 #undef DONTMASK
 	break;
     }
@@ -245,7 +270,63 @@ static void polypath_process_monitor_line(struct polypath *st, char *orgl)
 	abort();
     }
 
+#undef DONT
+
     /* OK, process it */
+    callback(st, bad,badctx, add,ifname,ifaddr,&ia,-1);
+
+ out:;
+}
+
+static void dump_pria(struct polypath *st, const char *ifname)
+{
+#ifdef POLYPATH_DEBUG
+    struct interf *interf;
+    if (ifname)
+	lg_perror(LG,M_DEBUG,0, "polypath record ifaddr `%s'",ifname);
+    LIST_FOREACH(interf, &st->interfs, entry) {
+	lg_perror(LG,M_DEBUG,0, "  polypath interface `%s', nsocks=%d",
+		  interf->name, interf->socks.n_socks);
+	int i;
+	for (i=0; i<interf->socks.n_socks; i++) {
+	    struct udpsock *us=&interf->socks.socks[i];
+	    lg_perror(LG,M_DEBUG,0, "    polypath sock fd=%d addr=%s",
+		      us->fd, iaddr_to_string(&us->addr));
+	}
+    }
+#endif
+}
+
+static bool_t polypath_make_socket(struct polypath *st,
+				   bad_fn_type *bad, void *badctx,
+				   struct udpsock *us, const char *ifname)
+    /* on error exit has called bad; might leave us->fd as -1 */
+{
+    assert(us->fd==-1);
+
+    bool_t ok=udp_make_socket(&st->uc,us,M_WARNING);
+    if (!ok) BAD("unable to set up socket");
+    int r=setsockopt(us->fd,SOL_SOCKET,SO_BINDTODEVICE,
+		     ifname,strlen(ifname)+1);
+    if (r) BADE("setsockopt(,,SO_BINDTODEVICE,)",errno);
+    return True;
+
+ out:
+    return False;
+}
+
+static void polypath_record_ifaddr(struct polypath *st,
+				   bad_fn_type *bad, void *badctx,
+				   bool_t add, const char *ifname,
+				   const char *ifaddr,
+				   const union iaddr *ia, int fd)
+{
+    struct udpcommon *uc=&st->uc;
+    struct interf *interf=0;
+    struct udpsock *us=0;
+
+    dump_pria(st,ifname);
+
     int n_ifs=0;
     LIST_FOREACH(interf,&st->interfs,entry) {
 	if (!strcmp(interf->name,ifname))
@@ -260,8 +341,8 @@ static void polypath_process_monitor_line(struct polypath *st, char *orgl)
     interf->socks.n_socks=0;
     FILLZERO(interf->experienced_xmit_noaf);
     LIST_INSERT_HEAD(&st->interfs,interf,entry);
-    udp_socks_register(&st->uc,&interf->socks);
     interf->name=strdup(ifname);
+    udp_socks_register(&st->uc,&interf->socks,interf->name);
     if (!interf->name) BADE("strdup interface name",errno);
  found_interf:
 
@@ -270,23 +351,29 @@ static void polypath_process_monitor_line(struct polypath *st, char *orgl)
 	    BAD("too many addresses on this interface");
 	struct udpsock *us=&interf->socks.socks[interf->socks.n_socks];
 	us->fd=-1;
-	COPY_OBJ(us->addr,ia);
-	bool_t ok=udp_make_socket(&st->uc,us,M_WARNING);
-	if (!ok) BAD("unable to set up socket");
-	r=setsockopt(us->fd,SOL_SOCKET,SO_BINDTODEVICE,
-		     ifname,strlen(ifname)+1);
-	if (r) BADE("setsockopt(,,SO_BINDTODEVICE,)",errno);
+	COPY_OBJ(us->addr,*ia);
+	if (fd<0) {
+	    bool_t ok=polypath_make_socket(st,bad,badctx, us,ifname);
+	    if (!ok) goto out;
+	} else {
+	    bool_t ok=udp_import_socket(uc,us,M_WARNING,fd);
+	    if (!ok) goto out;
+	    fd=-1;
+	}
 	interf->socks.n_socks++;
+	lg_perror(LG,M_INFO,0,"using %s %s",ifname,
+		  iaddr_to_string(&us->addr));
 	us=0; /* do not destroy this socket during `out' */
-	lg_perror(LG,M_INFO,0,"using %s %s",ifname,ifaddr);
     } else {
 	int i;
 	for (i=0; i<interf->socks.n_socks; i++)
-	    if (!memcmp(&interf->socks.socks[i].addr,&ia,sizeof(ia)))
+	    if (iaddr_equal(&interf->socks.socks[i].addr,ia,True))
 		goto address_remove_found;
-	BAD("address to remove not found");
+	bad(st,badctx,M_DEBUG,"address to remove not found",0);
+	goto out;
     address_remove_found:
-	lg_perror(LG,M_INFO,0,"removed %s %s",ifname,ifaddr);
+	lg_perror(LG,M_INFO,0,"removed %s %s",ifname,
+		  iaddr_to_string(&interf->socks.socks[i].addr));
 	udp_destroy_socket(&st->uc,&interf->socks.socks[i]);
 	interf->socks.socks[i]=
 	    interf->socks.socks[--interf->socks.n_socks];
@@ -295,6 +382,8 @@ static void polypath_process_monitor_line(struct polypath *st, char *orgl)
  out:
     if (us)
 	udp_destroy_socket(uc,us);
+    if (fd>=0)
+	close(fd);
     if (interf && !interf->socks.n_socks) {
 	udp_socks_deregister(&st->uc,&interf->socks);
 	LIST_REMOVE(interf,entry);
@@ -302,28 +391,13 @@ static void polypath_process_monitor_line(struct polypath *st, char *orgl)
 	free(interf);
     }
 
-    dump_ppml(st,0);
-
-#undef BAD
-#undef BADE
-#undef DONT
+    dump_pria(st,0);
 }
 
-static void polypath_afterpoll(void *state, struct pollfd *fds, int nfds)
+static void subproc_problem(struct polypath *st,
+			    enum async_linebuf_result alr, const char *emsg)
 {
-    struct polypath *st=state;
-    enum async_linebuf_result alr;
-    const char *emsg;
     int status;
-
-    if (nfds<1) return;
-
-    while ((alr=async_linebuf_read(fds,&st->lbuf,&emsg)) == async_linebuf_ok)
-	polypath_process_monitor_line(st,st->lbuf.base);
-
-    if (alr==async_linebuf_nothing)
-	return;
-
     assert(st->monitor_pid);
 
     pid_t gotpid=waitpid(st->monitor_pid,&status,WNOHANG);
@@ -339,13 +413,38 @@ static void polypath_afterpoll(void *state, struct pollfd *fds, int nfds)
 	lg_perror(LG,M_FATAL,0,"unexpected EOF from interface monitor");
     else
 	lg_perror(LG,M_FATAL,0,"bad output from interface monitor: %s",emsg);
-
     assert(!"not reached");
 }
 
+/* Used in non-privsep case, and in privsep child */
+static void afterpoll_monitor(struct polypath *st, struct pollfd *fd,
+			      polypath_ppml_callback_type *callback)
+{
+    enum async_linebuf_result alr;
+    const char *emsg;
+    
+    while ((alr=async_linebuf_read(fd,&st->lbuf,&emsg)) == async_linebuf_ok)
+	polypath_process_monitor_line(st,st->lbuf.base,callback);
+
+    if (alr==async_linebuf_nothing)
+	return;
+
+    subproc_problem(st,alr,emsg);
+}
+
+/* Used in non-privsep case only - glue for secnet main loop */
+static void polypath_afterpoll_monitor(void *state, struct pollfd *fds,
+				       int nfds)
+{
+    struct polypath *st=state;
+    if (nfds<1) return;
+    afterpoll_monitor(st,fds,polypath_record_ifaddr);
+}
+
 /* Actual udp packet sending work */
 static bool_t polypath_sendmsg(void *commst, struct buffer_if *buf,
-			  const struct comm_addr *dest)
+			  const struct comm_addr *dest,
+			  struct comm_clientinfo *clientinfo)
 {
     struct polypath *st=commst;
     struct interf *interf;
@@ -362,8 +461,8 @@ static bool_t polypath_sendmsg(void *commst, struct buffer_if *buf,
 	    attempted=True;
 	    int r=sendto(us->fd,buf->start,buf->size,
 			 0,&dest->ia.sa,iaddr_socklen(&dest->ia));
-	    udp_sock_experienced(0,&st->uc, interf->name,us,
-				 1,af, r,errno);
+	    udp_sock_experienced(0,&st->uc,&interf->socks,us,
+				 &dest->ia,af, r,errno);
 	    if (r>=0) {
 		reasonable=True;
 		break;
@@ -384,27 +483,37 @@ static bool_t polypath_sendmsg(void *commst, struct buffer_if *buf,
     return allreasonable;
 }
 
-static void polypath_phase_startmonitor(void *sst, uint32_t newphase)
+/* Non-privsep: called in (sole) child.  Privsep: in grandchild. */
+static void child_monitor(struct polypath *st, int childfd)
+{
+    dup2(childfd,1);
+    execvp(st->monitor_command[0],(char**)st->monitor_command);
+    fprintf(stderr,"secnet: cannot execute %s: %s\n",
+	    st->monitor_command[0], strerror(errno));
+    exit(-1);
+}
+
+/* General utility function. */
+static void start_subproc(struct polypath *st, void (*make_fdpair)(int[2]),
+			  void (*child)(struct polypath *st, int childfd),
+			  const char *desc)
 {
-    struct polypath *st=sst;
     int pfds[2];
 
     assert(!st->monitor_pid);
     assert(st->monitor_fd<0);
 
-    pipe_cloexec(pfds);
+    make_fdpair(pfds);
 
     pid_t pid=fork();
     if (!pid) {
 	afterfork();
-	dup2(pfds[1],1);
-	execvp(st->monitor_command[0],(char**)st->monitor_command);
-	fprintf(stderr,"secnet: cannot execute %s: %s\n",
-		st->monitor_command[0], strerror(errno));
-	exit(-1);
+	close(pfds[0]);
+	child(st,pfds[1]);
+	abort();
     }
     if (pid<0)
-	fatal_perror("%s: failed to fork for interface monitor",
+	fatal_perror("%s: failed to fork for interface monitoring",
 		     st->uc.cc.cl.description);
 
     close(pfds[1]);
@@ -412,7 +521,278 @@ static void polypath_phase_startmonitor(void *sst, uint32_t newphase)
     st->monitor_fd=pfds[0];
     setnonblock(st->monitor_fd);
 
-    register_for_poll(st,polypath_beforepoll,polypath_afterpoll,"polypath");
+    lg_perror(LG,M_NOTICE,0, "%s: spawning %s [pid %ld]",
+	      st->uc.cc.cl.description, desc, (long)st->monitor_pid);
+}
+
+/* Non-privsep only: glue for forking the monitor, from the main loop */
+static void polypath_phase_startmonitor(void *sst, uint32_t newphase)
+{
+    struct polypath *st=sst;
+    start_subproc(st,pipe_cloexec,child_monitor,
+		  "interface monitor (no privsep)");
+    register_for_poll(st,polypath_beforepoll,
+		      polypath_afterpoll_monitor,"polypath");
+}
+
+/*----- Privsep-only: -----*/
+
+/*
+ * We use two subprocesses, a child and a grandchild.  These are
+ * forked before secnet drops privilege.
+ *
+ * The grandchild is the same interface monitor helper script as used
+ * in the non-privsep case.  But its lines are read by the child
+ * instead of by the main secnet.  The child is responsible for
+ * creating the actual socket (binding it, etc.).  Each socket is
+ * passed to secnet proper via fd passing, along with a data message
+ * describing the interface name and address.  The child does not
+ * retain a list of current interfaces and addresses - it trusts the
+ * interface monitor to get that right.  secnet proper still maintains
+ * that data structure.
+ *
+ * The result is that much of the non-privsep code can be reused, but
+ * just plumbed together differently.
+ *
+ * The child does not retain the socket after passing it on.
+ * Interface removals are handled similarly but without any fd.
+ *
+ * The result is that the configuration's limits on which interfaces
+ * and ports secnet may use are enforced by the privileged child.
+ */
+
+struct privsep_mdata {
+    bool_t add;
+    char ifname[100];
+    union iaddr ia;
+};
+
+static void papp_bad(struct polypath *st, void *badctx,
+		     int mclass, const char *m, int ev)
+{
+    const struct privsep_mdata *mdata=(const void*)st->lbuf.start;
+    const char *addr_str=badctx;
+
+    lg_perror(LG,mclass,ev,
+	      "error processing polypath address change %s %s [%s]: %s",
+	      mdata->add ? "+" : "-",
+	      mdata->ifname, addr_str, m);
+}
+
+static void polypath_afterpoll_privsep(void *state, struct pollfd *fds,
+				       int nfds)
+/* In secnet proper; receives messages from child. */
+{
+    struct polypath *st=state;
+
+    if (nfds<1) return;
+
+    int revents=fds[0].revents;
+
+    const char *badbit=pollbadbit(revents);
+    if (badbit) subproc_problem(st,async_linebuf_broken,badbit);
+
+    if (!(revents & POLLIN)) return;
+
+    for (;;) {
+	if (st->lbuf.size==sizeof(struct privsep_mdata)) {
+	    const struct privsep_mdata *mdata=(const void*)st->lbuf.start;
+	    if (mdata->add && st->privsep_incoming_fd<0)
+		fatal("polypath (privsep): got add message data but no fd");
+	    if (!mdata->add && st->privsep_incoming_fd>=0)
+		fatal("polypath (privsep): got remove message data with fd");
+	    if (!memchr(mdata->ifname,0,sizeof(mdata->ifname)))
+		fatal("polypath (privsep): got ifname with no terminating nul");
+	    int af=mdata->ia.sa.sa_family;
+	    if (!(af==AF_INET6 || af==AF_INET))
+		fatal("polypath (privsep): got message data but bad AF %d",af);
+	    const char *addr_str=iaddr_to_string(&mdata->ia);
+	    polypath_record_ifaddr(st,papp_bad,(void*)addr_str,
+				   mdata->add,mdata->ifname,addr_str,
+				   &mdata->ia, st->privsep_incoming_fd);
+	    st->privsep_incoming_fd=-1;
+	    st->lbuf.size=0;
+	}
+	struct msghdr msg;
+	int fd;
+	size_t cmsgdatalen=sizeof(fd);
+	char cmsg_control_buf[CMSG_SPACE(cmsgdatalen)];
+	struct iovec iov;
+
+	FILLZERO(msg);
+	msg.msg_iov=&iov;
+	msg.msg_iovlen=1;
+
+	iov.iov_base=st->lbuf.start+st->lbuf.size;
+	iov.iov_len=sizeof(struct privsep_mdata)-st->lbuf.size;
+
+	if (st->privsep_incoming_fd<0) {
+	    msg.msg_control=cmsg_control_buf;
+	    msg.msg_controllen=sizeof(cmsg_control_buf);
+	}
+
+	ssize_t got=recvmsg(st->monitor_fd,&msg,0);
+	if (got<0) {
+	    if (errno==EINTR) continue;
+	    if (iswouldblock(errno)) break;
+	    fatal_perror("polypath (privsep): recvmsg failed");
+	}
+	if (got==0)
+	    subproc_problem(st,async_linebuf_eof,0);
+
+	st->lbuf.size+=got;
+
+	if (msg.msg_controllen) {
+	    size_t cmsgdatalen=sizeof(st->privsep_incoming_fd);
+	    struct cmsghdr *h=CMSG_FIRSTHDR(&msg);
+	    if (!(st->privsep_incoming_fd==-1 &&
+		  h &&
+		  h->cmsg_level==SOL_SOCKET &&
+		  h->cmsg_type==SCM_RIGHTS &&
+		  h->cmsg_len==CMSG_LEN(cmsgdatalen) &&
+		  !CMSG_NXTHDR(&msg,h)))
+		subproc_problem(st,async_linebuf_broken,"bad cmsg");
+	    memcpy(&st->privsep_incoming_fd,CMSG_DATA(h),cmsgdatalen);
+	    assert(st->privsep_incoming_fd>=0);
+	}
+
+    }
+}
+
+static void privsep_handle_ifaddr(struct polypath *st,
+				   bad_fn_type *bad, void *badctx,
+				   bool_t add, const char *ifname,
+				   const char *ifaddr,
+				   const union iaddr *ia, int fd_dummy)
+/* In child: handles discovered wanted interfaces, making sockets
+   and sending them to secnet proper. */
+{
+    struct msghdr msg;
+    struct iovec iov;
+    struct udpsock us={ .fd=-1 };
+    size_t cmsgdatalen=sizeof(us.fd);
+    char cmsg_control_buf[CMSG_SPACE(cmsgdatalen)];
+
+    assert(fd_dummy==-1);
+
+    struct privsep_mdata mdata;
+    FILLZERO(mdata);
+    mdata.add=add;
+
+    size_t l=strlen(ifname);
+    if (l>=sizeof(mdata.ifname)) BAD("interface name too long");
+    strcpy(mdata.ifname,ifname);
+
+    COPY_OBJ(mdata.ia,*ia);
+
+    iov.iov_base=&mdata;
+    iov.iov_len =sizeof(mdata);
+
+    FILLZERO(msg);
+    msg.msg_iov=&iov;
+    msg.msg_iovlen=1;
+
+    if (add) {
+	COPY_OBJ(us.addr,*ia);
+	bool_t ok=polypath_make_socket(st,bad,badctx,&us,ifname);
+	if (!ok) goto out;
+
+	msg.msg_control=cmsg_control_buf;
+	msg.msg_controllen=sizeof(cmsg_control_buf);
+
+	struct cmsghdr *h=CMSG_FIRSTHDR(&msg);
+	h->cmsg_level=SOL_SOCKET;
+	h->cmsg_type =SCM_RIGHTS;
+	h->cmsg_len  =CMSG_LEN(cmsgdatalen);
+	memcpy(CMSG_DATA(h),&us.fd,cmsgdatalen);
+    }
+
+    while (iov.iov_len) {
+	ssize_t got=sendmsg(st->privsep_ipcsock_fd,&msg,0);
+	if (got<0) {
+	    if (errno!=EINTR) fatal_perror("polypath privsep sendmsg");
+	    got=0;
+	} else {
+	    assert(got>0);
+	    assert((size_t)got<=iov.iov_len);
+	}
+	iov.iov_base=(char*)iov.iov_base+got;
+	iov.iov_len-=got;
+	msg.msg_control=0;
+	msg.msg_controllen=0;
+    }
+
+ out:
+    if (us.fd>=0) close(us.fd);
+}
+
+static void child_privsep(struct polypath *st, int ipcsockfd)
+/* Privsep child main loop. */
+{
+    struct pollfd fds[2];
+
+    enter_phase(PHASE_CHILDPERSIST);
+
+    st->privsep_ipcsock_fd=ipcsockfd;
+    start_subproc(st,pipe_cloexec,child_monitor,
+		  "interface monitor (grandchild)");
+    for (;;) {
+	int nfds=1;
+	int r=polypath_beforepoll(st,fds,&nfds,0);
+	assert(nfds==1);
+	assert(!r);
+
+	fds[1].fd=st->privsep_ipcsock_fd;
+	fds[1].events=POLLIN;
+
+	r=poll(fds,ARRAY_SIZE(fds),-1);
+
+	if (r<0) {
+	    if (errno==EINTR) continue;
+	    fatal_perror("polypath privsep poll");
+	}
+	if (fds[1].revents) {
+	    if (fds[1].revents & (POLLHUP|POLLIN)) {
+		polypath_phase_shutdown(st,PHASE_SHUTDOWN);
+		exit(0);
+	    }
+	    fatal("polypath privsep poll parent socket revents=%#x",
+		  fds[1].revents);
+	}
+	if (fds[0].revents & POLLNVAL)
+	    fatal("polypath privsep poll child socket POLLNVAL");
+	afterpoll_monitor(st,fds,privsep_handle_ifaddr);
+    }
+}
+
+static void privsep_socketpair(int *fd)
+{
+    int r=socketpair(AF_UNIX,SOCK_STREAM,0,fd);
+    if (r) fatal_perror("socketpair(AF_UNIX,SOCK_STREAM,,)");
+    setcloexec(fd[0]);
+    setcloexec(fd[1]);
+}
+
+static void polypath_phase_startprivsep(void *sst, uint32_t newphase)
+{
+    struct polypath *st=sst;
+
+    if (!will_droppriv()) {
+	add_hook(PHASE_RUN,          polypath_phase_startmonitor,st);
+	return;
+    }
+
+    start_subproc(st,privsep_socketpair,child_privsep,
+		  "socket generator (privsep interface handler)");
+
+    BUF_FREE(&st->lbuf);
+    buffer_destroy(&st->lbuf);
+    buffer_new(&st->lbuf,sizeof(struct privsep_mdata));
+    BUF_ALLOC(&st->lbuf,"polypath mdata buf");
+    st->privsep_incoming_fd=-1;
+
+    register_for_poll(st,polypath_beforepoll,
+		      polypath_afterpoll_privsep,"polypath");
 }
 
 static void polypath_phase_shutdown(void *sst, uint32_t newphase)
@@ -424,6 +804,20 @@ static void polypath_phase_shutdown(void *sst, uint32_t newphase)
     }
 }
 
+static void polypath_phase_childpersist(void *sst, uint32_t newphase)
+{
+    struct polypath *st=sst;
+    struct interf *interf;
+
+    LIST_FOREACH(interf,&st->interfs,entry)
+	udp_socks_childpersist(&st->uc,&interf->socks);
+}
+
+#undef BAD
+#undef BADE
+
+/*----- generic closure and module setup -----*/
+
 static list_t *polypath_apply(closure_t *self, struct cloc loc,
 			      dict_t *context, list_t *args)
 {
@@ -459,8 +853,10 @@ static list_t *polypath_apply(closure_t *self, struct cloc loc,
     st->monitor_fd=-1;
     st->monitor_pid=0;
 
-    add_hook(PHASE_RUN,         polypath_phase_startmonitor,st);
+    add_hook(PHASE_GETRESOURCES, polypath_phase_startprivsep,st);
+
     add_hook(PHASE_SHUTDOWN,    polypath_phase_shutdown,    st);
+    add_hook(PHASE_CHILDPERSIST,polypath_phase_childpersist,st);
 
     return new_closure(&cc->cl);
 }