properly handle point-to-point interfaces in getifaddrs()

With point-to-point interfaces, the IFA_ADDRESS netlink attribute
contains the peer address while an extra attribute IFA_LOCAL carries
the actual local interface address.

Both the glibc and uclibc implementations of getifaddrs() handle this
case by moving the ifa_addr contents to the broadcast/remote address
union and overwriting ifa_addr upon receipt of an IFA_LOCAL attribute.

This patch adds the same special treatment logic of IFA_LOCAL to
musl's implementation of getifaddrs() in order to align its behaviour
with that of uclibc and glibc.

Signed-off-by: Jo-Philipp Wich <jow@openwrt.org>

diff --git a/src/network/getifaddrs.c b/src/network/getifaddrs.c
index 89a8f72..fed75bd 100644 (file)
--- a/src/network/getifaddrs.c
+++ b/src/network/getifaddrs.c
@@ -162,13 +162,26 @@ static int netlink_msg_to_ifaddr(void *pctx, struct nlmsghdr *h)
                for (rta = NLMSG_RTA(h, sizeof(*ifa)); NLMSG_RTAOK(rta, h); rta = RTA_NEXT(rta)) {
                        switch (rta->rta_type) {
                        case IFA_ADDRESS:
-                               copy_addr(&ifs->ifa.ifa_addr, ifa->ifa_family, &ifs->addr, RTA_DATA(rta), RTA_DATALEN(rta), ifa->ifa_index);
+                               /* If ifa_addr is already set we, received an IFA_LOCAL before
+                                * so treat this as destination address */
+                               if (ifs->ifa.ifa_addr)
+                                       copy_addr(&ifs->ifa.ifa_dstaddr, ifa->ifa_family, &ifs->ifu, RTA_DATA(rta), RTA_DATALEN(rta), ifa->ifa_index);
+                               else
+                                       copy_addr(&ifs->ifa.ifa_addr, ifa->ifa_family, &ifs->addr, RTA_DATA(rta), RTA_DATALEN(rta), ifa->ifa_index);
                                break;
                        case IFA_BROADCAST:
-                               /* For point-to-point links this is peer, but ifa_broadaddr
-                                * and ifa_dstaddr are union, so this works for both.  */
                                copy_addr(&ifs->ifa.ifa_broadaddr, ifa->ifa_family, &ifs->ifu, RTA_DATA(rta), RTA_DATALEN(rta), ifa->ifa_index);
                                break;
+                       case IFA_LOCAL:
+                               /* If ifa_addr is set and we get IFA_LOCAL, assume we have
+                                * a point-to-point network. Move address to correct field. */
+                               if (ifs->ifa.ifa_addr) {
+                                       ifs->ifu = ifs->addr;
+                                       ifs->ifa.ifa_dstaddr = &ifs->ifu.sa;
+                                       memset(&ifs->addr, 0, sizeof(ifs->addr));
+                               }
+                               copy_addr(&ifs->ifa.ifa_addr, ifa->ifa_family, &ifs->addr, RTA_DATA(rta), RTA_DATALEN(rta), ifa->ifa_index);
+                               break;
                        case IFA_LABEL:
                                if (RTA_DATALEN(rta) < sizeof(ifs->name)) {
                                        memcpy(ifs->name, RTA_DATA(rta), RTA_DATALEN(rta));