[PATCH 1/2] Decode setsockopt() multicast arguments

[Ben Noordhuis]

A small test program follows:

  #include <sys/socket.h>
  #include <netinet/in.h>
  #include <arpa/inet.h>
  #include <stddef.h>

  int main(void) {
    int fd;
    struct ip_mreq m4;
    struct ipv6_mreq m6;
    fd = socket(AF_INET6, SOCK_DGRAM, 0);
    inet_aton("224.0.0.2", &m4.imr_multiaddr);
    inet_aton("0.0.0.0", &m4.imr_interface);
    inet_pton(AF_INET6, "ff01::c", &m6.ipv6mr_multiaddr);
    m6.ipv6mr_interface = 1;
    setsockopt(fd, SOL_IP, IP_ADD_MEMBERSHIP, &m4, 1);
    setsockopt(fd, SOL_IP, IP_DROP_MEMBERSHIP, &m4, 1);
    setsockopt(fd, SOL_IP, IP_ADD_MEMBERSHIP, &m4, sizeof(m4));
    setsockopt(fd, SOL_IP, IP_DROP_MEMBERSHIP, &m4, sizeof(m4));
    setsockopt(fd, SOL_IPV6, IPV6_ADD_MEMBERSHIP, &m6, 1);
    setsockopt(fd, SOL_IPV6, IPV6_DROP_MEMBERSHIP, &m6, 1);
    setsockopt(fd, SOL_IPV6, IPV6_ADD_MEMBERSHIP, &m6, sizeof(m6));
    setsockopt(fd, SOL_IPV6, IPV6_DROP_MEMBERSHIP, &m6, sizeof(m6));
    m6.ipv6mr_interface = 42;
    setsockopt(fd, SOL_IPV6, IPV6_ADD_MEMBERSHIP, &m6, sizeof(m6));
    setsockopt(fd, SOL_IPV6, IPV6_DROP_MEMBERSHIP, &m6, sizeof(m6));
    return 0;
  }

And prints the following output when traced:

  setsockopt(3, SOL_IP, IP_ADD_MEMBERSHIP, "\340", 1)
    = -1 EINVAL (Invalid argument)
  setsockopt(3, SOL_IP, IP_DROP_MEMBERSHIP, "\340", 1)
    = -1 EINVAL (Invalid argument)
  setsockopt(3, SOL_IP, IP_ADD_MEMBERSHIP,
    {imr_multiaddr=inet_addr("224.0.0.2"),
    imr_interface=inet_addr("0.0.0.0")}, 8) = 0
  setsockopt(3, SOL_IP, IP_DROP_MEMBERSHIP,
    {imr_multiaddr=inet_addr("224.0.0.2"),
    imr_interface=inet_addr("0.0.0.0")}, 8) = 0
  setsockopt(3, SOL_IPV6, IPV6_ADD_MEMBERSHIP, "\377", 1)
    = -1 EINVAL (Invalid argument)
  setsockopt(3, SOL_IPV6, IPV6_DROP_MEMBERSHIP, "\377", 1)
    = -1 EINVAL (Invalid argument)
  setsockopt(3, SOL_IPV6, IPV6_ADD_MEMBERSHIP,
    {ipv6mr_multiaddr=inet_pton("ff01::c"),
    ipv6mr_interface=if_nametoindex("lo")}, 20) = 0
  setsockopt(3, SOL_IPV6, IPV6_DROP_MEMBERSHIP,
    {ipv6mr_multiaddr=inet_pton("ff01::c"),
    ipv6mr_interface=if_nametoindex("lo")}, 20) = 0
  setsockopt(3, SOL_IPV6, IPV6_ADD_MEMBERSHIP,
    {ipv6mr_multiaddr=inet_pton("ff01::c"),
    ipv6mr_interface=42}, 20) = -1 ENODEV (No such device)
  setsockopt(3, SOL_IPV6, IPV6_DROP_MEMBERSHIP,
    {ipv6mr_multiaddr=inet_pton("ff01::c"),
    ipv6mr_interface=42}, 20) = -1 EADDRNOTAVAIL
    (Cannot assign requested address)

* net.c (sys_setsockopt): decode IP_ADD_MEMBERSHIP, IP_DROP_MEMBERSHIP,
  IPV6_ADD_MEMBERSHIP and IPV6_DROP_MEMBERSHIP arguments.

Signed-off-by: Ben Noordhuis <info at bnoordhuis.nl>
---
 net.c | 85 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 85 insertions(+)

diff --git a/net.c b/net.c
index 49185dc..f55c6af 100644
--- a/net.c
+++ b/net.c
@@ -1325,6 +1325,73 @@ sys_getsockopt(struct tcb *tcp)
 	return 0;
 }
 
+static void
+print_interface(unsigned int index)
+{
+#ifdef HAVE_IF_INDEXTONAME
+	char buf[IFNAMSIZ + 1];
+	if (if_indextoname(index, buf) == buf) {
+		tprints("if_nametoindex(");
+		print_quoted_string(buf, sizeof(buf), QUOTE_0_TERMINATED);
+		tprints(")");
+		return;
+	}
+#endif
+	tprintf("%u", index);
+}
+
+#ifdef IP_ADD_MEMBERSHIP
+static void
+print_mreq(struct tcb *tcp, long addr, int len)
+{
+	struct ip_mreq mreq;
+	if (len == sizeof(mreq) && umove(tcp, addr, &mreq) == 0) {
+		tprints("{imr_multiaddr=inet_addr(");
+		print_quoted_string(inet_ntoa(mreq.imr_multiaddr),
+				    16, QUOTE_0_TERMINATED);
+		tprints("), imr_interface=inet_addr(");
+		print_quoted_string(inet_ntoa(mreq.imr_interface),
+				    16, QUOTE_0_TERMINATED);
+		tprints(")}");
+	}
+	else {
+		printstr(tcp, addr, len);
+	}
+}
+#endif /* IP_ADD_MEMBERSHIP */
+
+#ifdef IPV6_ADD_MEMBERSHIP
+static void
+print_mreq6(struct tcb *tcp, long addr, int len)
+{
+#ifdef HAVE_INET_NTOP
+	struct ipv6_mreq mreq;
+	const struct in6_addr *in6;
+	char address[INET6_ADDRSTRLEN];
+
+	if (len != sizeof(mreq))
+		goto fail;
+
+	if (umove(tcp, addr, &mreq) < 0)
+		goto fail;
+
+	in6 = &mreq.ipv6mr_multiaddr;
+	if (inet_ntop(AF_INET6, in6, address, sizeof(address)) != address)
+		goto fail;
+
+	tprints("{ipv6mr_multiaddr=inet_pton(");
+	print_quoted_string(address, sizeof(address), QUOTE_0_TERMINATED);
+	tprints("), ipv6mr_interface=");
+	print_interface(mreq.ipv6mr_interface);
+	tprints("}");
+	return;
+
+fail:
+#endif /* HAVE_INET_NTOP */
+	printstr(tcp, addr, len);
+}
+#endif /* IPV6_ADD_MEMBERSHIP */
+
 #ifdef MCAST_JOIN_GROUP
 static void
 print_group_req(struct tcb *tcp, long addr, int len)
@@ -1438,6 +1505,12 @@ print_setsockopt(struct tcb *tcp, int level, int name, long addr, int len)
 
 	case SOL_IP:
 		switch (name) {
+#ifdef IP_ADD_MEMBERSHIP
+		case IP_ADD_MEMBERSHIP:
+		case IP_DROP_MEMBERSHIP:
+			print_mreq(tcp, addr, len);
+			goto done;
+#endif /* IP_ADD_MEMBERSHIP */
 #ifdef MCAST_JOIN_GROUP
 		case MCAST_JOIN_GROUP:
 		case MCAST_LEAVE_GROUP:
@@ -1445,6 +1518,18 @@ print_setsockopt(struct tcb *tcp, int level, int name, long addr, int len)
 			goto done;
 #endif /* MCAST_JOIN_GROUP */
 		}
+		break;
+
+	case SOL_IPV6:
+		switch (name) {
+#ifdef IPV6_ADD_MEMBERSHIP
+		case IPV6_ADD_MEMBERSHIP:
+		case IPV6_DROP_MEMBERSHIP:
+			print_mreq6(tcp, addr, len);
+			goto done;
+#endif /* IPV6_ADD_MEMBERSHIP */
+		}
+		break;
 
 	case SOL_PACKET:
 		switch (name) {
-- 
2.1.0