git: be7bdb1cf0b0 - main - netinet: do route lookup when asked to join multicast group on ifindex 0
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Date: Wed, 15 Oct 2025 18:55:33 UTC
The branch main has been updated by glebius:
URL: https://cgit.FreeBSD.org/src/commit/?id=be7bdb1cf0b0f665bcd57c03fde41bd6c01d8ead
commit be7bdb1cf0b0f665bcd57c03fde41bd6c01d8ead
Author: Gleb Smirnoff <glebius@FreeBSD.org>
AuthorDate: 2025-10-15 18:54:57 +0000
Commit: Gleb Smirnoff <glebius@FreeBSD.org>
CommitDate: 2025-10-15 18:54:57 +0000
netinet: do route lookup when asked to join multicast group on ifindex 0
The code to do the route lookup was already there, but was used only for
the legacy IP_ADD_MEMBERSHIP when called without index. Do same lookup
for IP_ADD_MEMBERSHIP with index and what is more important for
MCAST_JOIN_GROUP, if the supplied index is 0. This is a neat feature and
Linux does that, so this should make a few applications easier portable to
FreeBSD.
Differential Revision: https://reviews.freebsd.org/D52918
---
sys/netinet/in_mcast.c | 113 ++++++++++++++--------------------
tests/sys/netinet/multicast-receive.c | 16 +++--
tests/sys/netinet/multicast.sh | 47 ++++++++++++++
3 files changed, 104 insertions(+), 72 deletions(-)
diff --git a/sys/netinet/in_mcast.c b/sys/netinet/in_mcast.c
index f5b20c49ffd2..ba112afbf002 100644
--- a/sys/netinet/in_mcast.c
+++ b/sys/netinet/in_mcast.c
@@ -159,9 +159,6 @@ static struct ip_moptions *
static int inp_get_source_filters(struct inpcb *, struct sockopt *);
static int inp_join_group(struct inpcb *, struct sockopt *);
static int inp_leave_group(struct inpcb *, struct sockopt *);
-static struct ifnet *
- inp_lookup_mcast_ifp(const struct inpcb *,
- const struct sockaddr_in *, const struct in_addr);
static int inp_block_unblock_source(struct inpcb *, struct sockopt *);
static int inp_set_multicast_if(struct inpcb *, struct sockopt *);
static int inp_set_source_filters(struct inpcb *, struct sockopt *);
@@ -1832,69 +1829,55 @@ inp_getmoptions(struct inpcb *inp, struct sockopt *sopt)
}
/*
- * Look up the ifnet to use for a multicast group membership,
- * given the IPv4 address of an interface, and the IPv4 group address.
- *
- * This routine exists to support legacy multicast applications
- * which do not understand that multicast memberships are scoped to
- * specific physical links in the networking stack, or which need
- * to join link-scope groups before IPv4 addresses are configured.
- *
- * Use this socket's current FIB number for any required FIB lookup.
- * If ina is INADDR_ANY, look up the group address in the unicast FIB,
- * and use its ifp; usually, this points to the default next-hop.
- *
- * If the FIB lookup fails, attempt to use the first non-loopback
- * interface with multicast capability in the system as a
- * last resort. The legacy IPv4 ASM API requires that we do
- * this in order to allow groups to be joined when the routing
- * table has not yet been populated during boot.
- *
- * Returns NULL if no ifp could be found, otherwise return referenced ifp.
+ * Look up the ifnet to join a multicast group membership via legacy
+ * IP_ADD_MEMBERSHIP or via more modern MCAST_JOIN_GROUP.
*
- * FUTURE: Implement IPv4 source-address selection.
+ * If the interface index was specified explicitly, just use it. If the
+ * address was specified (legacy), try to find matching interface. Else
+ * (index == 0 && no address) do a route lookup. If that fails for a modern
+ * MCAST_JOIN_GROUP return failure, for legacy IP_ADD_MEMBERSHIP find first
+ * multicast capable interface.
*/
static struct ifnet *
-inp_lookup_mcast_ifp(const struct inpcb *inp,
- const struct sockaddr_in *gsin, const struct in_addr ina)
+inp_lookup_mcast_ifp(const struct inpcb *inp, const struct in_addr maddr,
+const struct in_addr *ina, const u_int index)
{
struct ifnet *ifp;
struct nhop_object *nh;
NET_EPOCH_ASSERT();
- KASSERT(inp != NULL, ("%s: inp must not be NULL", __func__));
- KASSERT(gsin->sin_family == AF_INET, ("%s: not AF_INET", __func__));
- KASSERT(IN_MULTICAST(ntohl(gsin->sin_addr.s_addr)),
- ("%s: not multicast", __func__));
- ifp = NULL;
- if (!in_nullhost(ina)) {
- INADDR_TO_IFP(ina, ifp);
+ if (index != 0)
+ return (ifnet_byindex_ref(index));
+
+ if (ina != NULL && !in_nullhost(*ina)) {
+ INADDR_TO_IFP(*ina, ifp);
if (ifp != NULL)
if_ref(ifp);
- } else {
- nh = fib4_lookup(inp->inp_inc.inc_fibnum, gsin->sin_addr, 0, NHR_NONE, 0);
- if (nh != NULL) {
- ifp = nh->nh_ifp;
- if_ref(ifp);
- } else {
- struct in_ifaddr *ia;
- struct ifnet *mifp;
-
- mifp = NULL;
- CK_STAILQ_FOREACH(ia, &V_in_ifaddrhead, ia_link) {
- mifp = ia->ia_ifp;
- if (!(mifp->if_flags & IFF_LOOPBACK) &&
- (mifp->if_flags & IFF_MULTICAST)) {
- ifp = mifp;
- if_ref(ifp);
- break;
- }
+ return (ifp);
+ }
+
+ nh = fib4_lookup(inp->inp_inc.inc_fibnum, maddr, 0, NHR_NONE, 0);
+ if (nh != NULL) {
+ ifp = nh->nh_ifp;
+ if_ref(ifp);
+ return (ifp);
+ }
+
+ if (ina != NULL) {
+ struct in_ifaddr *ia;
+
+ CK_STAILQ_FOREACH(ia, &V_in_ifaddrhead, ia_link) {
+ if (!(ia->ia_ifp->if_flags & IFF_LOOPBACK) &&
+ (ia->ia_ifp->if_flags & IFF_MULTICAST)) {
+ ifp = ia->ia_ifp;
+ if_ref(ifp);
+ return (ifp);
}
}
}
- return (ifp);
+ return (NULL);
}
/*
@@ -1926,13 +1909,13 @@ inp_join_group(struct inpcb *inp, struct sockopt *sopt)
switch (sopt->sopt_name) {
case IP_ADD_MEMBERSHIP: {
struct ip_mreqn mreqn;
+ bool mreq;
- if (sopt->sopt_valsize == sizeof(struct ip_mreqn))
- error = sooptcopyin(sopt, &mreqn,
- sizeof(struct ip_mreqn), sizeof(struct ip_mreqn));
- else
- error = sooptcopyin(sopt, &mreqn,
- sizeof(struct ip_mreq), sizeof(struct ip_mreq));
+ mreq = (sopt->sopt_valsize != sizeof(struct ip_mreqn));
+
+ error = sooptcopyin(sopt, &mreqn,
+ mreq ? sizeof(struct ip_mreq) : sizeof(struct ip_mreqn),
+ mreq ? sizeof(struct ip_mreq) : sizeof(struct ip_mreqn));
if (error)
return (error);
@@ -1943,12 +1926,9 @@ inp_join_group(struct inpcb *inp, struct sockopt *sopt)
return (EINVAL);
NET_EPOCH_ENTER(et);
- if (sopt->sopt_valsize == sizeof(struct ip_mreqn) &&
- mreqn.imr_ifindex != 0)
- ifp = ifnet_byindex_ref(mreqn.imr_ifindex);
- else
- ifp = inp_lookup_mcast_ifp(inp, &gsa->sin,
- mreqn.imr_address);
+ ifp = inp_lookup_mcast_ifp(inp, mreqn.imr_multiaddr,
+ mreq ? &mreqn.imr_address : NULL,
+ mreq ? 0 : mreqn.imr_ifindex);
NET_EPOCH_EXIT(et);
break;
}
@@ -1971,8 +1951,8 @@ inp_join_group(struct inpcb *inp, struct sockopt *sopt)
ssa->sin.sin_addr = mreqs.imr_sourceaddr;
NET_EPOCH_ENTER(et);
- ifp = inp_lookup_mcast_ifp(inp, &gsa->sin,
- mreqs.imr_interface);
+ ifp = inp_lookup_mcast_ifp(inp, mreqs.imr_multiaddr,
+ &mreqs.imr_interface, 0);
NET_EPOCH_EXIT(et);
CTR3(KTR_IGMPV3, "%s: imr_interface = 0x%08x, ifp = %p",
__func__, ntohl(mreqs.imr_interface.s_addr), ifp);
@@ -2013,7 +1993,8 @@ inp_join_group(struct inpcb *inp, struct sockopt *sopt)
return (EINVAL);
NET_EPOCH_ENTER(et);
- ifp = ifnet_byindex_ref(gsr.gsr_interface);
+ ifp = inp_lookup_mcast_ifp(inp, gsa->sin.sin_addr, NULL,
+ gsr.gsr_interface);
NET_EPOCH_EXIT(et);
if (ifp == NULL)
return (EADDRNOTAVAIL);
diff --git a/tests/sys/netinet/multicast-receive.c b/tests/sys/netinet/multicast-receive.c
index 81d0f10f5cfe..62fc68200dd6 100644
--- a/tests/sys/netinet/multicast-receive.c
+++ b/tests/sys/netinet/multicast-receive.c
@@ -36,6 +36,7 @@
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
+#include <sysexits.h>
#include <limits.h>
#include <err.h>
@@ -93,8 +94,9 @@ usage:
.imr_multiaddr = maddr,
.imr_interface = ifaddr,
};
- assert(setsockopt(s, IPPROTO_IP, IP_ADD_MEMBERSHIP, &mreq,
- sizeof(mreq)) == 0);
+ if (setsockopt(s, IPPROTO_IP, IP_ADD_MEMBERSHIP, &mreq,
+ sizeof(mreq)) != 0)
+ err(EX_OSERR, "setsockopt");
} else if (strcmp(argv[1], "ip_mreqn") == 0) {
/*
* ip_mreqn shall be used with index, but for testing
@@ -105,8 +107,9 @@ usage:
.imr_address = index ? (struct in_addr){ 0 } : ifaddr,
.imr_ifindex = index ? ifindex : 0,
};
- assert(setsockopt(s, IPPROTO_IP, IP_ADD_MEMBERSHIP, &mreqn,
- sizeof(mreqn)) == 0);
+ if (setsockopt(s, IPPROTO_IP, IP_ADD_MEMBERSHIP, &mreqn,
+ sizeof(mreqn)) != 0)
+ err(EX_OSERR, "setsockopt");
} else if (strcmp(argv[1], "group_req") == 0) {
if (!index)
errx(1, "group_req expects index");
@@ -116,8 +119,9 @@ usage:
gsa->sin_family = AF_INET;
gsa->sin_len = sizeof(struct sockaddr_in);
gsa->sin_addr = maddr;
- assert(setsockopt(s, IPPROTO_IP, MCAST_JOIN_GROUP, &greq,
- sizeof(greq)) == 0);
+ if (setsockopt(s, IPPROTO_IP, MCAST_JOIN_GROUP, &greq,
+ sizeof(greq)) != 0)
+ err(EX_OSERR, "setsockopt");
} else
goto usage;
diff --git a/tests/sys/netinet/multicast.sh b/tests/sys/netinet/multicast.sh
index 273970d0f7ea..34094ff08705 100755
--- a/tests/sys/netinet/multicast.sh
+++ b/tests/sys/netinet/multicast.sh
@@ -79,6 +79,27 @@ IP_ADD_MEMBERSHIP_ip_mreq_body()
0.0.0.0 6676 233.252.0.1 6676 192.0.3.1 hello
atf_check -s exit:0 sh -c "wait $pid; exit $?"
atf_check -s exit:0 -o inline:"192.0.3.1:6676 hello\n" cat out
+
+ # join group on the first multicast capable interface (epair1a)
+ multicast_join ip_mreq 0.0.0.0
+ atf_check -s exit:0 -o empty \
+ jexec mjail1 $(atf_get_srcdir)/multicast-send \
+ 0.0.0.0 6676 233.252.0.1 6676 192.0.2.1 hello
+ atf_check -s exit:0 sh -c "wait $pid; exit $?"
+ atf_check -s exit:0 -o inline:"192.0.2.1:6676 hello\n" cat out
+
+ # Set up the receiving jail so that first multicast capable interface
+ # is epair1a and default route points into epair2a. This will allow us
+ # to exercise both branches of inp_lookup_mcast_ifp().
+ jexec mjail2 route add default 192.0.3.254
+
+ # join group on the interface determined by the route lookup
+ multicast_join ip_mreq 0.0.0.0
+ atf_check -s exit:0 -o empty \
+ jexec mjail1 $(atf_get_srcdir)/multicast-send \
+ 0.0.0.0 6676 233.252.0.1 6676 192.0.3.1 hello
+ atf_check -s exit:0 sh -c "wait $pid; exit $?"
+ atf_check -s exit:0 -o inline:"192.0.3.1:6676 hello\n" cat out
}
IP_ADD_MEMBERSHIP_ip_mreq_cleanup()
{
@@ -111,6 +132,19 @@ IP_ADD_MEMBERSHIP_ip_mreqn_body()
0.0.0.0 6676 233.252.0.1 6676 ${epair2}a hello
atf_check -s exit:0 sh -c "wait $pid; exit $?"
atf_check -s exit:0 -o inline:"192.0.3.1:6676 hello\n" cat out
+
+ # try to join group on the interface determined by the route lookup
+ atf_check -s exit:71 -e inline:"multicast-receive: setsockopt: Can't assign requested address\n" \
+ jexec mjail2 $(atf_get_srcdir)/multicast-receive \
+ ip_mreqn 233.252.0.1 6676 0
+ # add route and try again
+ jexec mjail2 route add default 192.0.3.254
+ multicast_join ip_mreqn 0
+ atf_check -s exit:0 -o empty \
+ jexec mjail1 $(atf_get_srcdir)/multicast-send \
+ 0.0.0.0 6676 233.252.0.1 6676 192.0.3.1 hello
+ atf_check -s exit:0 sh -c "wait $pid; exit $?"
+ atf_check -s exit:0 -o inline:"192.0.3.1:6676 hello\n" cat out
}
IP_ADD_MEMBERSHIP_ip_mreqn_cleanup()
{
@@ -143,6 +177,19 @@ MCAST_JOIN_GROUP_body()
0.0.0.0 6676 233.252.0.1 6676 ${epair2}a hello
atf_check -s exit:0 sh -c "wait $pid; exit $?"
atf_check -s exit:0 -o inline:"192.0.3.1:6676 hello\n" cat out
+
+ # try to join group on the interface determined by the route lookup
+ atf_check -s exit:71 -e inline:"multicast-receive: setsockopt: Can't assign requested address\n" \
+ jexec mjail2 $(atf_get_srcdir)/multicast-receive \
+ group_req 233.252.0.1 6676 0
+ # add route and try again
+ jexec mjail2 route add default 192.0.3.254
+ multicast_join group_req 0
+ atf_check -s exit:0 -o empty \
+ jexec mjail1 $(atf_get_srcdir)/multicast-send \
+ 0.0.0.0 6676 233.252.0.1 6676 192.0.3.1 hello
+ atf_check -s exit:0 sh -c "wait $pid; exit $?"
+ atf_check -s exit:0 -o inline:"192.0.3.1:6676 hello\n" cat out
}
MCAST_JOIN_GROUP_cleanup()
{