This patch introduces a mode where we only forward loopback connections
and traffic between two namespaces (via the loopback interface, 'lo'),
without a tap device.
It might be used to fix up podman IPv4 / IPv6 loopback mapping when using
rootlesskit for forwarding ports, or a way to implement isolated containers.
In this mode, --host-lo-to-ns-lo and --no-icmp are automatically enabled.
Option --no-splice is rejected.
Link: https://bugs.passt.top/show_bug.cgi?id=149
Signed-off-by: Yumei Huang
---
conf.c | 39 ++++++++++++++++++++++++++++-----------
fwd.c | 3 +++
passt.1 | 5 +++++
passt.h | 2 ++
pasta.c | 3 +++
tap.c | 11 +++++++----
6 files changed, 48 insertions(+), 15 deletions(-)
diff --git a/conf.c b/conf.c
index dbff87c..9d88ad7 100644
--- a/conf.c
+++ b/conf.c
@@ -1059,7 +1059,8 @@ pasta_opts:
" --no-copy-addrs DEPRECATED:\n"
" Don't copy all addresses to namespace\n"
" --ns-mac-addr ADDR Set MAC address on tap interface\n"
- " --no-splice Disable inbound socket splicing\n");
+ " --no-splice Disable inbound socket splicing\n"
+ " --splice-only Only enable loopback forwarding\n");
passt_exit(status);
}
@@ -1142,7 +1143,7 @@ static void conf_print(const struct ctx *c)
inet_ntop(AF_INET6, &c->ip6.addr_out, buf6, sizeof(buf6)));
}
- if (c->mode == MODE_PASTA)
+ if (c->mode == MODE_PASTA && !c->splice_only)
info("Namespace interface: %s", c->pasta_ifn);
info("MAC:");
@@ -1465,6 +1466,7 @@ void conf(struct ctx *c, int argc, char **argv)
{"no-ndp", no_argument, &c->no_ndp, 1 },
{"no-ra", no_argument, &c->no_ra, 1 },
{"no-splice", no_argument, &c->no_splice, 1 },
+ {"splice-only", no_argument, &c->splice_only, 1 },
{"freebind", no_argument, &c->freebind, 1 },
{"no-map-gw", no_argument, &no_map_gw, 1 },
{"ipv4-only", no_argument, NULL, '4' },
@@ -1961,8 +1963,11 @@ void conf(struct ctx *c, int argc, char **argv)
}
} while (name != -1);
- if (c->mode != MODE_PASTA)
+ if (c->mode != MODE_PASTA) {
c->no_splice = 1;
+ if (c->splice_only)
+ die("--splice-only is for pasta mode only");
+ }
if (c->mode == MODE_PASTA && !c->pasta_conf_ns) {
if (copy_routes_opt)
@@ -1971,6 +1976,16 @@ void conf(struct ctx *c, int argc, char **argv)
die("--no-copy-addrs needs --config-net");
}
+ if (c->mode == MODE_PASTA && c->splice_only) {
+ if (c->no_splice)
+ die("--splice-only is incompatible with --no-splice");
+
+ c->host_lo_to_ns_lo = 1;
+ c->no_icmp = 1;
+ c->no_dns = 1;
+ c->no_dns_search = 1;
+ }
+
if (!ifi4 && *c->ip4.ifname_out)
ifi4 = if_nametoindex(c->ip4.ifname_out);
@@ -1994,9 +2009,9 @@ void conf(struct ctx *c, int argc, char **argv)
log_conf_parsed = true; /* Stop printing everything */
nl_sock_init(c, false);
- if (!v6_only)
+ if (!v6_only && !c->splice_only)
c->ifi4 = conf_ip4(ifi4, &c->ip4);
- if (!v4_only)
+ if (!v4_only && !c->splice_only)
c->ifi6 = conf_ip6(ifi6, &c->ip6);
if (c->ifi4 && c->mtu < IPV4_MIN_MTU) {
@@ -2018,16 +2033,18 @@ void conf(struct ctx *c, int argc, char **argv)
}
if (!c->ifi4 && !v6_only) {
- info("IPv4: no external interface as template, use local mode");
-
- conf_ip4_local(&c->ip4);
+ if (!c->splice_only) {
+ info("IPv4: no external interface as template, use local mode");
+ conf_ip4_local(&c->ip4);
+ }
c->ifi4 = -1;
}
if (!c->ifi6 && !v4_only) {
- info("IPv6: no external interface as template, use local mode");
-
- conf_ip6_local(&c->ip6);
+ if (!c->splice_only) {
+ info("IPv6: no external interface as template, use local mode");
+ conf_ip6_local(&c->ip6);
+ }
c->ifi6 = -1;
}
diff --git a/fwd.c b/fwd.c
index 961c533..6cdb197 100644
--- a/fwd.c
+++ b/fwd.c
@@ -771,6 +771,9 @@ uint8_t fwd_nat_from_host(const struct ctx *c, uint8_t proto,
return PIF_SPLICE;
}
+ if (c->splice_only)
+ return PIF_NONE;
+
if (!nat_inbound(c, &ini->eaddr, &tgt->oaddr)) {
if (inany_v4(&ini->eaddr)) {
if (IN4_IS_ADDR_UNSPECIFIED(&c->ip4.our_tap_addr))
diff --git a/passt.1 b/passt.1
index db0d662..8e8e179 100644
--- a/passt.1
+++ b/passt.1
@@ -755,6 +755,11 @@ Default is to let the tap driver build a pseudorandom hardware address.
Disable the bypass path for inbound, local traffic. See the section \fBHandling
of local traffic in pasta\fR in the \fBNOTES\fR for more details.
+.TP
+.BR \-\-splice-only
+Do not create a tap device in the namespace. In this mode, \fIpasta\fR only
+forwards loopback traffic between namespaces.
+
.SH EXAMPLES
.SS \fBpasta
diff --git a/passt.h b/passt.h
index f3664ce..299185b 100644
--- a/passt.h
+++ b/passt.h
@@ -200,6 +200,7 @@ struct ip6_ctx {
* @no_ndp: Disable NDP handler altogether
* @no_ra: Disable router advertisements
* @no_splice: Disable socket splicing for inbound traffic
+ * @splice_only: Only enable loopback forwarding
* @host_lo_to_ns_lo: Map host loopback addresses to ns loopback addresses
* @freebind: Allow binding of non-local addresses for forwarding
* @low_wmem: Low probed net.core.wmem_max
@@ -277,6 +278,7 @@ struct ctx {
int no_ndp;
int no_ra;
int no_splice;
+ int splice_only;
int host_lo_to_ns_lo;
int freebind;
diff --git a/pasta.c b/pasta.c
index 0ddd6b0..bab945f 100644
--- a/pasta.c
+++ b/pasta.c
@@ -316,6 +316,9 @@ void pasta_ns_conf(struct ctx *c)
die("Couldn't bring up loopback interface in namespace: %s",
strerror_(-rc));
+ if (c->splice_only)
+ return;
+
/* Get or set MAC in target namespace */
if (MAC_IS_ZERO(c->guest_mac))
nl_link_get_mac(nl_sock_ns, c->pasta_ifi, c->guest_mac);
diff --git a/tap.c b/tap.c
index 9d1344b..eaa6111 100644
--- a/tap.c
+++ b/tap.c
@@ -1491,13 +1491,16 @@ static int tap_ns_tun(void *arg)
*/
static void tap_sock_tun_init(struct ctx *c)
{
- NS_CALL(tap_ns_tun, c);
- if (c->fd_tap == -1)
- die("Failed to set up tap device in namespace");
+ if (!c->splice_only) {
+ NS_CALL(tap_ns_tun, c);
+ if (c->fd_tap == -1)
+ die("Failed to set up tap device in namespace");
+ }
pasta_ns_conf(c);
- tap_start_connection(c);
+ if (!c->splice_only)
+ tap_start_connection(c);
}
/**
--
2.49.0