[RFCLAT#9] refactor getinterface_ip() to stop using libnl
The interface address query doesn't use libnl anymore.
Needed for reducing the library dependency. Once the last libnl user
del_anycast_address() is removed, clatd can remove libnl. Less
dependency helps moving clatd to mainline.
parse_ifaddrmsg() is used to replaced with getaddr_cb() which updates
struct target variable until walking through all messages.
parse_ifaddrmsg() keeps the same behavior as getaddr_cb().
Bug: 212345928
Test: atest clatd_test and manual test
1. Connect to ipv6-only wifi.
2. Try IPv4 traffic.
$ ping 8.8.8.8
Change-Id: I56591ec851d3202e18cce9fce3995d658d9f07e2
diff --git a/getaddr.c b/getaddr.c
index 6f4bc86..f25efc1 100644
--- a/getaddr.c
+++ b/getaddr.c
@@ -15,21 +15,27 @@
*
* getaddr.c - get a locally configured address
*/
-#include <net/if.h>
-#include <netinet/in.h>
-#include <string.h>
-#include <strings.h>
+#include "getaddr.h"
+#include <errno.h>
#include <linux/if_addr.h>
#include <linux/rtnetlink.h>
+#include <net/if.h>
+#include <netinet/in.h>
#include <netlink/handlers.h>
#include <netlink/msg.h>
+#include <string.h>
+#include <strings.h>
+#include <unistd.h>
-#include "getaddr.h"
#include "logging.h"
-#include "netlink_msg.h"
-// shared state between getinterface_ip and getaddr_cb
+// Kernel suggests that keep the packet under 8KiB (NLMSG_GOODSIZE) in include/linux/netlink.h.
+#define NLMSG_SIZE 8192
+
+// shared state between getinterface_ip and parse_ifaddrmsg
+// TODO: refactor the communication between getinterface_ip and parse_ifaddrmsg because there
+// is no netlink callback anymore.
struct target {
int family;
unsigned int ifindex;
@@ -37,57 +43,97 @@
int foundip;
};
-/* function: getaddr_cb
- * callback for getinterface_ip
- * msg - netlink message
- * data - (struct target) info for which address we're looking for
+/* function: parse_ifaddrmsg
+ * parse ifaddrmsg for getinterface_ip
+ * nh - netlink message header
+ * targ_p - (struct target) info for which address we're looking for
+ * and the parsed result if any.
*/
-static int getaddr_cb(struct nl_msg *msg, void *data) {
+static void parse_ifaddrmsg(struct nlmsghdr *nh, struct target *targ_p) {
struct ifaddrmsg *ifa_p;
struct rtattr *rta_p;
int rta_len;
- struct target *targ_p = (struct target *)data;
- ifa_p = (struct ifaddrmsg *)nlmsg_data(nlmsg_hdr(msg));
+ ifa_p = (struct ifaddrmsg *)NLMSG_DATA(nh);
rta_p = (struct rtattr *)IFA_RTA(ifa_p);
- if (ifa_p->ifa_index != targ_p->ifindex) return NL_OK;
+ if (ifa_p->ifa_index != targ_p->ifindex) return;
- if (ifa_p->ifa_scope != RT_SCOPE_UNIVERSE) return NL_OK;
+ if (ifa_p->ifa_scope != RT_SCOPE_UNIVERSE) return;
- rta_len = RTM_PAYLOAD(nlmsg_hdr(msg));
+ rta_len = IFA_PAYLOAD(nh);
for (; RTA_OK(rta_p, rta_len); rta_p = RTA_NEXT(rta_p, rta_len)) {
switch (rta_p->rta_type) {
case IFA_ADDRESS:
if ((targ_p->family == AF_INET6) && !(ifa_p->ifa_flags & IFA_F_SECONDARY)) {
memcpy(&targ_p->ip.ip6, RTA_DATA(rta_p), rta_p->rta_len - sizeof(struct rtattr));
targ_p->foundip = 1;
- return NL_OK;
+ return;
}
break;
case IFA_LOCAL:
if (targ_p->family == AF_INET) {
memcpy(&targ_p->ip.ip4, RTA_DATA(rta_p), rta_p->rta_len - sizeof(struct rtattr));
targ_p->foundip = 1;
- return NL_OK;
+ return;
}
break;
}
}
-
- return NL_OK;
}
-/* function: error_handler
- * error callback for getinterface_ip
- * nla - source of the error message
- * err - netlink message
- * arg - (struct target) info for which address we're looking for
- */
-static int error_handler(__attribute__((unused)) struct sockaddr_nl *nla,
- __attribute__((unused)) struct nlmsgerr *err,
- __attribute__((unused)) void *arg) {
- return NL_OK;
+void sendrecv_ifaddrmsg(struct target *targ_p) {
+ int s = socket(PF_NETLINK, SOCK_DGRAM | SOCK_CLOEXEC, NETLINK_ROUTE);
+ if (s < 0) {
+ logmsg(ANDROID_LOG_ERROR, "open NETLINK_ROUTE socket failed %s", strerror(errno));
+ return;
+ }
+
+ // Fill in netlink structures.
+ struct {
+ struct nlmsghdr n;
+ struct ifaddrmsg r;
+ } req = {
+ // Netlink message header.
+ .n.nlmsg_len = NLMSG_LENGTH(sizeof(struct ifaddrmsg)),
+ .n.nlmsg_flags = NLM_F_REQUEST | NLM_F_ROOT,
+ .n.nlmsg_type = RTM_GETADDR,
+
+ // Interface address message header.
+ .r.ifa_family = targ_p->family,
+ };
+
+ // Send interface address message.
+ if ((send(s, &req, req.n.nlmsg_len, 0)) < 0) {
+ logmsg(ANDROID_LOG_ERROR, "send netlink socket failed %s", strerror(errno));
+ close(s);
+ return;
+ }
+
+ // Read interface address message and parse the result if any.
+ ssize_t bytes_read;
+ char buf[NLMSG_SIZE];
+ while ((bytes_read = recv(s, buf, sizeof(buf), 0)) > 0) {
+ struct nlmsghdr *nh = (struct nlmsghdr *)buf;
+ for (; NLMSG_OK(nh, bytes_read); nh = NLMSG_NEXT(nh, bytes_read)) {
+ if (nh->nlmsg_type == NLMSG_DONE) {
+ close(s);
+ return;
+ }
+ if (nh->nlmsg_type == NLMSG_ERROR) {
+ logmsg(ANDROID_LOG_ERROR, "netlink message error");
+ close(s);
+ return;
+ }
+ if (nh->nlmsg_type == RTM_NEWADDR) {
+ // Walk through the all messages and update struct target variable as the deleted
+ // callback behavior of getaddr_cb() which always returns NL_OK.
+ // TODO: review if this can early return once address has been found.
+ parse_ifaddrmsg(nh, targ_p);
+ }
+ }
+ }
+ close(s);
}
/* function: getinterface_ip
@@ -97,42 +143,28 @@
* family - family
*/
union anyip *getinterface_ip(const char *interface, int family) {
- struct ifaddrmsg ifa;
- struct nl_cb *callbacks = NULL;
- struct target targ;
union anyip *retval = NULL;
+ struct target targ = {
+ .family = family,
+ .foundip = 0,
+ .ifindex = if_nametoindex(interface),
+ };
- targ.family = family;
- targ.foundip = 0;
- targ.ifindex = if_nametoindex(interface);
if (targ.ifindex == 0) {
return NULL; // interface not found
}
- memset(&ifa, 0, sizeof(ifa));
- ifa.ifa_family = targ.family;
-
- callbacks = nl_cb_alloc(NL_CB_DEFAULT);
- if (!callbacks) {
- goto cleanup;
- }
- nl_cb_set(callbacks, NL_CB_VALID, NL_CB_CUSTOM, getaddr_cb, &targ);
- nl_cb_err(callbacks, NL_CB_CUSTOM, error_handler, &targ);
-
- // sends message and waits for a response
- send_ifaddrmsg(RTM_GETADDR, NLM_F_REQUEST | NLM_F_ROOT, &ifa, callbacks);
+ // sends message and receives the response.
+ sendrecv_ifaddrmsg(&targ);
if (targ.foundip) {
retval = malloc(sizeof(union anyip));
if (!retval) {
logmsg(ANDROID_LOG_FATAL, "getinterface_ip/out of memory");
- goto cleanup;
+ return NULL;
}
memcpy(retval, &targ.ip, sizeof(union anyip));
}
-cleanup:
- if (callbacks) nl_cb_put(callbacks);
-
return retval;
}