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Rewrite the netlink handling code to use libmnl. The size cost is very small,

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and it is hard to do netlink completely correctly as it is poorly documented.
This commit is contained in:
Nicholas J. Kain
2011-07-02 01:34:50 -04:00
parent 38ad2399ed
commit 17570e9a38
5 changed files with 269 additions and 326 deletions
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2
CMakeLists.txt
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@@ -7,6 +7,8 @@ set(CMAKE_CXX_FLAGS "${CMAKE_C_FLAGS} -s -std=gnu99 -pedantic -Wall -lcap -DHAVE
include_directories("${PROJECT_SOURCE_DIR}/ncmlib")
add_subdirectory(ncmlib)
include_directories("${PROJECT_SOURCE_DIR}/libmnl")
add_subdirectory(libmnl)
add_subdirectory(ifchd)
add_subdirectory(ndhc)

2
ndhc/CMakeLists.txt
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@@ -5,4 +5,4 @@ cmake_minimum_required (VERSION 2.6)
file(GLOB NDHC_SRCS "*.c")
add_executable(ndhc ${NDHC_SRCS})
target_link_libraries(ndhc ncmlib)
target_link_libraries(ndhc ncmlib libmnl)

4
ndhc/ndhc.c
View File

@@ -314,7 +314,5 @@ int main(int argc, char **argv)
ifchange(NULL, IFCHANGE_DECONFIG);
do_work();
nl_close(&cs);
return EXIT_SUCCESS;
return EXIT_SUCCESS; // Never reached.
}

276
ndhc/netlink.c
View File

@@ -1,9 +1,6 @@
/* netlink.c - netlink physical link notification handling and info retrieval
*
* (c) 2011 Nicholas J. Kain <njkain at gmail dot com>
* (c) 2006-2007 Stefan Rompf <sux@loplof.de>
*
* This code was largely taken from Stefan Rompf's dhcpclient.
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
@@ -34,14 +31,15 @@
#include <string.h>
#include <sys/select.h>
#include <fcntl.h>
#include <time.h>
#include <libmnl/libmnl.h>
#include <errno.h>
#include "netlink.h"
#include "ifchange.h"
#include "arp.h"
#include "log.h"
#define NLMSG_RECVSIZE 8192
enum {
IFS_NONE = 0,
IFS_UP,
@@ -50,76 +48,34 @@ enum {
IFS_REMOVED
};
static unsigned int nl_seq;
static struct mnl_socket *mls;
/* internal callback handling */
static void (*nlcb_function)(struct nlmsghdr *msg, void **args);
static void *nlcb_args[3];
static __u32 nlcb_pid;
static unsigned int nlcb_seq;
static char nlcb_run;
static void nl_close(struct client_state_t *cs)
{
mnl_socket_close(mls);
cs->nlFd = -1;
}
int nl_open(struct client_state_t *cs)
{
struct sockaddr_nl nlsock = {
.nl_family = AF_NETLINK,
.nl_pad = 0,
.nl_pid = getpid(),
.nl_groups = RTMGRP_LINK
};
nlcb_pid = nlsock.nl_pid;
assert(cs->nlFd == -1);
cs->nlFd = socket(AF_NETLINK, SOCK_DGRAM, NETLINK_ROUTE);
if (cs->nlFd == -1)
if ((mls = mnl_socket_open(NETLINK_ROUTE)) == (struct mnl_socket *)-1)
return -1;
if (bind(cs->nlFd, (const struct sockaddr *)&nlsock, sizeof(nlsock)))
goto err_close;
cs->nlFd = mnl_socket_get_fd(mls);
if (fcntl(cs->nlFd, F_SETFD, FD_CLOEXEC))
goto err_close;
if (mnl_socket_bind(mls, RTMGRP_LINK, 0))
goto err_close;
return 0;
err_close:
nl_close(cs);
return -1;
}
void nl_close(struct client_state_t *cs)
{
close(cs->nlFd);
cs->nlFd = -1;
}
void nl_queryifstatus(int ifidx, struct client_state_t *cs)
{
struct {
struct nlmsghdr hdr;
struct ifinfomsg ifinfo;
} req;
req.hdr.nlmsg_len = sizeof req;
req.hdr.nlmsg_type = RTM_GETLINK;
req.hdr.nlmsg_flags = NLM_F_REQUEST | NLM_F_ROOT;
req.hdr.nlmsg_seq = ++nl_seq;
req.hdr.nlmsg_pid = nlcb_pid;
req.ifinfo.ifi_family = AF_UNSPEC;
req.ifinfo.ifi_index = ifidx; /* Doesn't work... */
req.ifinfo.ifi_flags = IFF_UP;
req.ifinfo.ifi_change = 0xffffffff;
send(cs->nlFd, &req, sizeof req, 0);
}
static void takedown_if(struct client_state_t *cs)
{
log_line("nl: taking down interface");
// Same as packet.c: line 258
// XXX: Same as packet.c - merge somehow?
ifchange(NULL, IFCHANGE_DECONFIG);
cs->dhcpState = DS_SELECTING;
cs->timeout = 0;
@@ -128,53 +84,99 @@ static void takedown_if(struct client_state_t *cs)
set_listen_raw(cs);
}
// Decode netlink messages and process them
static void nl_handlemsg(struct nlmsghdr *msg, unsigned int len,
struct client_state_t *cs)
static int data_attr_cb(const struct nlattr *attr, void *data)
{
if (len < sizeof(*msg)) return;
const struct nlattr **tb = data;
int type = mnl_attr_get_type(attr);
while(NLMSG_OK(msg,len)) {
if (nlcb_run &&
nlcb_pid == msg->nlmsg_pid &&
nlcb_seq == msg->nlmsg_seq) {
nlcb_function(msg, nlcb_args);
if (msg->nlmsg_type == NLMSG_DONE ||
msg->nlmsg_type == NLMSG_ERROR) nlcb_run = 0;
/* skip unsupported attribute in user-space */
if (mnl_attr_type_valid(attr, IFLA_MAX) < 0)
return MNL_CB_OK;
switch (type) {
case IFLA_IFNAME:
if (mnl_attr_validate(attr, MNL_TYPE_STRING) < 0) {
log_warning("nl: IFLA_IFNAME failed validation.");
return MNL_CB_ERROR;
}
break;
case IFLA_ADDRESS:
if (mnl_attr_validate(attr, MNL_TYPE_STRING) < 0) {
log_warning("nl: IFLA_ADDRESS failed validation.");
return MNL_CB_ERROR;
}
break;
}
tb[type] = attr;
return MNL_CB_OK;
}
if (NLMSG_PAYLOAD(msg, msg->nlmsg_len) >= sizeof(struct ifinfomsg)) {
struct ifinfomsg *ifinfo = NLMSG_DATA(msg);
static void get_if_index_and_mac(const struct nlmsghdr *nlh,
struct ifinfomsg *ifm,
const struct nlattr **tb)
{
mnl_attr_parse(nlh, sizeof(*ifm), data_attr_cb, tb);
if (!tb[IFLA_IFNAME])
return;
if (!strcmp(client_config.interface, mnl_attr_get_str(tb[IFLA_IFNAME]))) {
client_config.ifindex = ifm->ifi_index;
if (!tb[IFLA_ADDRESS])
suicide("FATAL: adapter %s lacks a hardware address");
int maclen = mnl_attr_get_len(tb[IFLA_ADDRESS]) - 4;
if (maclen != 6)
suicide("FATAL: adapter hardware address length should be 6, but is %u",
maclen);
switch(msg->nlmsg_type) {
const unsigned char *mac =
(unsigned char *)mnl_attr_get_str(tb[IFLA_ADDRESS]);
log_line("%s hardware address %x:%x:%x:%x:%x:%x",
client_config.interface,
mac[0], mac[1], mac[2], mac[3], mac[4], mac[5]);
memcpy(client_config.arp, mac, 6);
}
}
// XXX: Rather than exit, go into RELEASE state until a new hardware event
// forces wakeup.
static int data_cb(const struct nlmsghdr *nlh, void *data)
{
struct nlattr *tb[IFLA_MAX+1] = {0};
struct ifinfomsg *ifm = mnl_nlmsg_get_payload(nlh);
struct client_state_t *cs = data;
switch(nlh->nlmsg_type) {
case RTM_NEWLINK:
if (ifinfo->ifi_index != client_config.ifindex)
if (!client_config.ifindex)
get_if_index_and_mac(nlh, ifm, (const struct nlattr **)tb);
if (ifm->ifi_index != client_config.ifindex)
break;
if (ifinfo->ifi_flags & IFF_UP) {
if (ifinfo->ifi_flags & IFF_RUNNING) {
if (ifm->ifi_flags & IFF_UP) {
if (ifm->ifi_flags & IFF_RUNNING) {
if (cs->ifsPrevState != IFS_UP) {
cs->ifsPrevState = IFS_UP;
/*
* If we have a lease, then check to see
* if our gateway is still valid (via ARP).
* If it fails, state -> INIT.
*
* If we don't have a lease, state -> INIT.
*/
// If we have a lease, then check to see
// if our gateway is still valid (via ARP).
// If it fails, state -> SELECTING.
if (cs->dhcpState == DS_BOUND) {
if (arp_gw_check(cs) == -1)
log_warning("arp_gw_check could not make arp socket, assuming lease is still OK");
} else if (cs->dhcpState != DS_SELECTING)
log_warning("nl: arp_gw_check could not make arp socket, assuming lease is still OK");
else
log_line("nl: interface back, revalidating lease");
// If we don't have a lease, state -> SELECTING.
} else if (cs->dhcpState != DS_SELECTING) {
log_line("nl: interface back, querying for new lease");
takedown_if(cs);
}
}
} else {
if (cs->ifsPrevState != IFS_DOWN) {
// Interface was marked up but not running.
// Get a new lease from scratch.
cs->ifsPrevState = IFS_DOWN;
takedown_if(cs);
}
}
} else {
// No hardware carrier.
if (cs->ifsPrevState != IFS_SHUT) {
cs->ifsPrevState = IFS_SHUT;
log_line("Interface shut down; exiting.");
@@ -183,7 +185,7 @@ static void nl_handlemsg(struct nlmsghdr *msg, unsigned int len,
}
break;
case RTM_DELLINK:
if (ifinfo->ifi_index != client_config.ifindex)
if (ifm->ifi_index != client_config.ifindex)
break;
if (cs->ifsPrevState != IFS_REMOVED) {
cs->ifsPrevState = IFS_REMOVED;
@@ -194,95 +196,41 @@ static void nl_handlemsg(struct nlmsghdr *msg, unsigned int len,
default:
break;
}
}
msg = NLMSG_NEXT(msg,len);
}
return MNL_CB_OK;
}
void handle_nl_message(struct client_state_t *cs)
{
char c[NLMSG_RECVSIZE];
struct nlmsghdr *msg = (struct nlmsghdr *)c;
int n;
char buf[MNL_SOCKET_BUFFER_SIZE];
int ret;
assert(cs->nlFd != -1);
n = recv(cs->nlFd, c, NLMSG_RECVSIZE, 0);
nl_handlemsg(msg, n, cs);
do {
ret = mnl_socket_recvfrom(mls, buf, sizeof buf);
ret = mnl_cb_run(buf, ret, 0, 0, data_cb, cs);
} while (ret > 0);
if (ret == -1)
log_line("nl callback function returned error: %s", strerror(errno));
}
// Wait for and synchronously process netlink replies until a callback completes
static void nl_sync_dump(struct client_state_t *cs)
{
char c[NLMSG_RECVSIZE];
struct nlmsghdr *msg = (struct nlmsghdr *)c;
int n;
nlcb_seq = nl_seq;
for(nlcb_run = 1; nlcb_run;) {
n = recv(cs->nlFd, c, NLMSG_RECVSIZE, 0);
assert(n >= 0);
nl_handlemsg(msg, n, cs);
}
}
// Callback function for getting interface mac address and index.
static void copy_ifdata(struct nlmsghdr *msg, void **args)
{
struct ifinfomsg *ifinfo = NLMSG_DATA(msg);
struct rtattr *rta = IFLA_RTA(ifinfo);
int len = NLMSG_PAYLOAD(msg, sizeof(*ifinfo));
int found = 0;
if (msg->nlmsg_type != RTM_NEWLINK)
return;
if (client_config.ifindex)
return;
for(; RTA_OK(rta, len); rta = RTA_NEXT(rta, len)) {
switch(rta->rta_type) {
case IFLA_IFNAME:
if (!strncmp(client_config.interface,
(char *)RTA_DATA(rta), RTA_PAYLOAD(rta))) {
client_config.ifindex = ifinfo->ifi_index;
found |= 1;
}
break;
case IFLA_ADDRESS:
if (found != 1)
break;
/* We can only handle ethernet like devices with 6 octet MAC */
if (RTA_PAYLOAD(rta) == 6) {
memcpy(client_config.arp, RTA_DATA(rta), 6);
found |= 2;
}
break;
}
}
if (found == 3)
nlcb_args[0] = (void *)1;
}
// Gets interface mac address and index (synchronous).
int nl_getifdata(const char *ifname, struct client_state_t *cs)
{
struct {
struct nlmsghdr hdr;
struct ifinfomsg ifinfo;
} req;
char buf[MNL_SOCKET_BUFFER_SIZE];
struct nlmsghdr *nlh;
struct ifinfomsg *ifinfo;
unsigned int seq;
req.hdr.nlmsg_len = sizeof(req);
req.hdr.nlmsg_type = RTM_GETLINK;
req.hdr.nlmsg_flags = NLM_F_REQUEST | NLM_F_ROOT;
req.hdr.nlmsg_seq = ++nl_seq;
req.hdr.nlmsg_pid = nlcb_pid;
req.ifinfo.ifi_family = AF_UNSPEC;
nlh = mnl_nlmsg_put_header(buf);
nlh->nlmsg_type = RTM_GETLINK;
nlh->nlmsg_flags = NLM_F_REQUEST | NLM_F_ROOT;
nlh->nlmsg_seq = seq = time(NULL);
if (send(cs->nlFd, &req, sizeof(req), 0) != sizeof(req)) return -1;
ifinfo = mnl_nlmsg_put_extra_header(nlh, sizeof(struct ifinfomsg));
ifinfo->ifi_family = AF_UNSPEC;
nlcb_function = copy_ifdata;
nlcb_args[0] = NULL;
if (mnl_socket_sendto(mls, nlh, nlh->nlmsg_len) < 0)
return -1;
nl_sync_dump(cs);
return nlcb_args[0]?0:-1;
handle_nl_message(cs);
return 0;
}

5
ndhc/netlink.h
View File

@@ -1,9 +1,6 @@
/* netlink.h - netlink physical link notification handling and info retrieval
*
* (c) 2011 Nicholas J. Kain <njkain at gmail dot com>
* (c) 2006-2007 Stefan Rompf <sux@loplof.de>
*
* This code was largely taken from Stefan Rompf's dhcpclient.
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
@@ -26,8 +23,6 @@
#include "state.h"
int nl_open(struct client_state_t *cs);
void nl_close(struct client_state_t *cs);
void nl_queryifstatus(int ifidx, struct client_state_t *cs);
void handle_nl_message(struct client_state_t *cs);
int nl_getifdata(const char *ifname, struct client_state_t *cs);