add basic support for jail network namespaces

Prepare netifd for handling procd service jails having their own
network namespace.
Intefaces having the jail attribute will only be brought inside the
jail's network namespace by procd calling the newly introduced ubus
method 'netns_updown'.
Currently proto 'static' is supported and configuration changes are
not yet being handled (ie. you'll have to restart the jailed service
for changes to take effect).

Example /etc/config/network snippet:

config device 'veth0'
    option type 'veth'
    option name 'vhost0'
    option peer_name 'virt0'

config interface 'virt'
    option type 'bridge'
    list ifname 'vhost0'
    option proto 'static'
    option ipaddr '10.0.0.1'
    option netmask '255.255.255.0'

config interface 'virt0'
    option ifname 'virt0'
    option proto 'static'
    option ipaddr '10.0.0.2'
    option netmask '255.255.255.0'
    option gateway '10.0.0.1'
    option dns '10.0.0.1'
    option jail 'transmission'

Signed-off-by: Daniel Golle <daniel@makrotopia.org>

1 files changed, 30 insertions, 13 deletions

diff --git a/interface-ip.c b/interface-ip.c
index c159e09..91c305b 100644
--- a/interface-ip.c
+++ b/interface-ip.c
@@ -15,6 +15,8 @@
 #include <string.h>
 #include <stdlib.h>
 #include <stdio.h>
+#include <libgen.h>
+#include <sys/stat.h>
 
 #include <limits.h>
 #include <arpa/inet.h>
@@ -1443,7 +1445,7 @@ static int resolv_conf_iface_cmp(const void *k1, const void *k2, void *ptr)
 }
 
 static void
-__interface_write_dns_entries(FILE *f)
+__interface_write_dns_entries(FILE *f, const char *jail)
 {
 	struct interface *iface;
 	struct {
@@ -1457,6 +1459,9 @@ __interface_write_dns_entries(FILE *f)
 		if (iface->state != IFS_UP)
 			continue;
 
+		if (jail && (!iface->jail || strcmp(jail, iface->jail)))
+			continue;
+
 		if (vlist_simple_empty(&iface->proto_ip.dns_search) &&
 		    vlist_simple_empty(&iface->proto_ip.dns_servers) &&
 		    vlist_simple_empty(&iface->config_ip.dns_search) &&
@@ -1488,21 +1493,33 @@ __interface_write_dns_entries(FILE *f)
 }
 
 void
-interface_write_resolv_conf(void)
+interface_write_resolv_conf(const char *jail)
 {
-	char *path = alloca(strlen(resolv_conf) + 5);
+	size_t plen = (jail ? strlen(jail) + 1 : 0 ) + strlen(resolv_conf) + 1;
+	char *path = alloca(plen);
+	char *dpath = alloca(plen);
+	char *tmppath = alloca(plen + 4);
 	FILE *f;
 	uint32_t crcold, crcnew;
 
-	sprintf(path, "%s.tmp", resolv_conf);
-	unlink(path);
-	f = fopen(path, "w+");
+	if (jail) {
+		sprintf(path, "/tmp/resolv.conf-%s.d/resolv.conf.auto", jail);
+		strcpy(dpath, path);
+		dpath = dirname(dpath);
+		mkdir(dpath, 0755);
+	} else {
+		strcpy(path, resolv_conf);
+	}
+
+	sprintf(tmppath, "%s.tmp", path);
+	unlink(tmppath);
+	f = fopen(tmppath, "w+");
 	if (!f) {
 		D(INTERFACE, "Failed to open %s for writing\n", path);
 		return;
 	}
 
-	__interface_write_dns_entries(f);
+	__interface_write_dns_entries(f, jail);
 
 	fflush(f);
 	rewind(f);
@@ -1510,17 +1527,17 @@ interface_write_resolv_conf(void)
 	fclose(f);
 
 	crcold = crcnew + 1;
-	f = fopen(resolv_conf, "r");
+	f = fopen(path, "r");
 	if (f) {
 		crcold = crc32_file(f);
 		fclose(f);
 	}
 
 	if (crcold == crcnew) {
-		unlink(path);
-	} else if (rename(path, resolv_conf) < 0) {
-		D(INTERFACE, "Failed to replace %s\n", resolv_conf);
-		unlink(path);
+		unlink(tmppath);
+	} else if (rename(tmppath, path) < 0) {
+		D(INTERFACE, "Failed to replace %s\n", path);
+		unlink(tmppath);
 	}
 }
 
@@ -1640,7 +1657,7 @@ interface_ip_update_complete(struct interface_ip_settings *ip)
 	vlist_flush(&ip->addr);
 	vlist_flush(&ip->prefix);
 	vlist_flush(&ip->neighbor);
-	interface_write_resolv_conf();
+	interface_write_resolv_conf(ip->iface->jail);
 }
 
 void