Use native netlink code instead of /sbin/ip to manipulate routes
Shelling out to /sbin/ip is slow, and more importantly it does
not preserve the error messages returned by the kernel when
adding or deleting a route fails. Instead, use netlink directly.
This change does not yet pass the errors back to CommandListener;
that is done in the next change in the series.
Change-Id: I5ad3c8583580857be6386a620ff5c4f3872d685b
diff --git a/server/RouteController.cpp b/server/RouteController.cpp
index b44a31a..3c16fa3 100644
--- a/server/RouteController.cpp
+++ b/server/RouteController.cpp
@@ -19,10 +19,21 @@
#include "Fwmark.h"
#include "NetdConstants.h"
+#include <arpa/inet.h>
+#include <errno.h>
+#include <linux/netlink.h>
#include <linux/rtnetlink.h>
#include <logwrap/logwrap.h>
#include <map>
+#include <netinet/in.h>
#include <net/if.h>
+#include <sys/socket.h>
+#include <sys/uio.h>
+#include <unistd.h>
+
+// Avoids "non-constant-expression cannot be narrowed from type 'unsigned int' to 'unsigned short'"
+// warnings when using RTA_LENGTH(x) inside static initializers (even when x is already uint16_t).
+#define U16_RTA_LENGTH(x) static_cast<uint16_t>(RTA_LENGTH((x)))
namespace {
@@ -109,30 +120,106 @@
return true;
}
-bool runIpRouteCommand(const char* action, uint32_t table, const char* interface,
- const char* destination, const char* nexthop) {
- char tableString[UINT32_STRLEN];
- snprintf(tableString, sizeof(tableString), "%u", table);
+// Adds or deletes an IPv4 or IPv6 route.
+// Returns 0 on success or negative errno on failure.
+int modifyIpRoute(uint16_t action, uint32_t table, const char* interface, const char* destination,
+ const char* nexthop) {
+ // At least the destination must be non-null.
+ if (!destination) {
+ return -EFAULT;
+ }
- int argc = 0;
- const char* argv[16];
+ // Parse the prefix.
+ uint8_t rawAddress[sizeof(in6_addr)];
+ uint8_t family, prefixLength;
+ int rawLength = parsePrefix(destination, &family, rawAddress, sizeof(rawAddress),
+ &prefixLength);
+ if (rawLength < 0) {
+ return rawLength;
+ }
- argv[argc++] = IP_PATH;
- argv[argc++] = "route";
- argv[argc++] = action;
- argv[argc++] = "table";
- argv[argc++] = tableString;
- if (destination) {
- argv[argc++] = destination;
- argv[argc++] = "dev";
- argv[argc++] = interface;
- if (nexthop) {
- argv[argc++] = "via";
- argv[argc++] = nexthop;
+ if (static_cast<size_t>(rawLength) > sizeof(rawAddress)) {
+ return -ENOBUFS; // Cannot happen; parsePrefix only supports IPv4 and IPv6.
+ }
+
+ // If an interface was specified, find the ifindex.
+ uint32_t ifindex;
+ if (interface) {
+ ifindex = if_nametoindex(interface);
+ if (!ifindex) {
+ return -ENODEV;
}
}
- return !android_fork_execvp(argc, const_cast<char**>(argv), NULL, false, false);
+ // If a nexthop was specified, parse it as the same family as the prefix.
+ uint8_t rawNexthop[sizeof(in6_addr)];
+ if (nexthop && !inet_pton(family, nexthop, rawNexthop)) {
+ return -EINVAL;
+ }
+
+ // Assemble a netlink request and put it in an array of iovec structures.
+ nlmsghdr nlmsg = {
+ .nlmsg_type = action,
+ .nlmsg_flags = NLM_F_REQUEST | NLM_F_ACK,
+ };
+ rtmsg rtmsg = {
+ .rtm_protocol = RTPROT_STATIC,
+ .rtm_type = RTN_UNICAST,
+ .rtm_family = family,
+ .rtm_dst_len = prefixLength,
+ };
+ rtattr rta_table = { U16_RTA_LENGTH(sizeof(table)), RTA_TABLE };
+ rtattr rta_oif = { U16_RTA_LENGTH(sizeof(ifindex)), RTA_OIF };
+ rtattr rta_dst = { U16_RTA_LENGTH(rawLength), RTA_DST };
+ rtattr rta_gateway = { U16_RTA_LENGTH(rawLength), RTA_GATEWAY };
+ if (action == RTM_NEWROUTE) {
+ nlmsg.nlmsg_flags |= (NLM_F_CREATE | NLM_F_EXCL);
+ }
+
+ iovec iov[] = {
+ { &nlmsg, sizeof(nlmsg) },
+ { &rtmsg, sizeof(rtmsg) },
+ { &rta_table, sizeof(rta_table) },
+ { &table, sizeof(table) },
+ { &rta_dst, sizeof(rta_dst) },
+ { rawAddress, static_cast<size_t>(rawLength) },
+ { &rta_oif, interface ? sizeof(rta_oif) : 0 },
+ { &ifindex, interface ? sizeof(interface) : 0 },
+ { &rta_gateway, nexthop ? sizeof(rta_gateway) : 0 },
+ { rawNexthop, nexthop ? static_cast<size_t>(rawLength) : 0 },
+ };
+ int iovlen = ARRAY_SIZE(iov);
+
+ for (int i = 0; i < iovlen; ++i) {
+ nlmsg.nlmsg_len += iov[i].iov_len;
+ }
+
+ int ret;
+ struct {
+ nlmsghdr msg;
+ nlmsgerr err;
+ } response;
+
+ sockaddr_nl kernel = {AF_NETLINK, 0, 0, 0};
+ int sock = socket(AF_NETLINK, SOCK_DGRAM, NETLINK_ROUTE);
+ if (sock != -1 &&
+ connect(sock, reinterpret_cast<sockaddr *>(&kernel), sizeof(kernel)) != -1 &&
+ writev(sock, iov, iovlen) != -1 &&
+ (ret = recv(sock, &response, sizeof(response), 0)) != -1) {
+ if (ret == sizeof(response)) {
+ ret = response.err.error; // Netlink errors are negative errno.
+ } else {
+ ret = -EBADMSG;
+ }
+ } else {
+ ret = -errno;
+ }
+
+ if (sock != -1) {
+ close(sock);
+ }
+
+ return ret;
}
bool modifyPerNetworkRules(unsigned netId, const char* interface, Permission permission, bool add,
@@ -223,7 +310,7 @@
}
bool modifyRoute(const char* interface, const char* destination, const char* nexthop,
- const char* action, RouteController::TableType tableType, unsigned /* uid */) {
+ int action, RouteController::TableType tableType, unsigned /* uid */) {
uint32_t table = 0;
switch (tableType) {
case RouteController::INTERFACE: {
@@ -245,7 +332,7 @@
return false;
}
- if (!runIpRouteCommand(action, table, interface, destination, nexthop)) {
+ if (modifyIpRoute(action, table, interface, destination, nexthop)) {
return false;
}
@@ -258,7 +345,7 @@
// them based on the return status of the 'ip' command. Fix this situation by ignoring errors
// only when action == ADD && error == EEXIST.
if (!nexthop && !strchr(destination, ':')) {
- runIpRouteCommand(action, RT_TABLE_MAIN, interface, destination, NULL);
+ modifyIpRoute(action, RT_TABLE_MAIN, interface, destination, NULL);
}
return true;
@@ -365,10 +452,10 @@
bool RouteController::addRoute(const char* interface, const char* destination,
const char* nexthop, TableType tableType, unsigned uid) {
- return modifyRoute(interface, destination, nexthop, ADD, tableType, uid);
+ return modifyRoute(interface, destination, nexthop, RTM_NEWROUTE, tableType, uid);
}
bool RouteController::removeRoute(const char* interface, const char* destination,
const char* nexthop, TableType tableType, unsigned uid) {
- return modifyRoute(interface, destination, nexthop, DEL, tableType, uid);
+ return modifyRoute(interface, destination, nexthop, RTM_DELROUTE, tableType, uid);
}