nexmon – Rev 1
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/*
* Copyright (c) 2011 Jakub Zawadzki
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. The name of the author may not be used to endorse or promote
* products derived from this software without specific prior written
* permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
* OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#ifdef HAVE_CONFIG_H
#include "config.h"
#endif
#include "pcap-int.h"
#ifdef NEED_STRERROR_H
#include "strerror.h"
#endif
#include <errno.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include <time.h>
#include <sys/time.h>
#include <netinet/in.h>
#include <linux/types.h>
#include <linux/netlink.h>
#include <linux/netfilter.h>
#include <linux/netfilter/nfnetlink.h>
#include <linux/netfilter/nfnetlink_log.h>
#include <linux/netfilter/nfnetlink_queue.h>
/* NOTE: if your program drops privilages after pcap_activate() it WON'T work with nfqueue.
* It took me quite some time to debug ;/
*
* Sending any data to nfnetlink socket requires CAP_NET_ADMIN privilages,
* and in nfqueue we need to send verdict reply after recving packet.
*
* In tcpdump you can disable dropping privilages with -Z root
*/
#include "pcap-netfilter-linux.h"
#define HDR_LENGTH (NLMSG_LENGTH(NLMSG_ALIGN(sizeof(struct nfgenmsg))))
#define NFLOG_IFACE "nflog"
#define NFQUEUE_IFACE "nfqueue"
typedef enum { OTHER = -1, NFLOG, NFQUEUE } nftype_t;
/*
* Private data for capturing on Linux netfilter sockets.
*/
struct pcap_netfilter {
u_int packets_read; /* count of packets read with recvfrom() */
};
static int nfqueue_send_verdict(const pcap_t *handle, u_int16_t group_id, u_int32_t id, u_int32_t verdict);
static int
netfilter_read_linux(pcap_t *handle, int max_packets, pcap_handler callback, u_char *user)
{
struct pcap_netfilter *handlep = handle->priv;
const unsigned char *buf;
int count = 0;
int len;
/* ignore interrupt system call error */
do {
len = recv(handle->fd, handle->buffer, handle->bufsize, 0);
if (handle->break_loop) {
handle->break_loop = 0;
return -2;
}
} while ((len == -1) && (errno == EINTR));
if (len < 0) {
snprintf(handle->errbuf, PCAP_ERRBUF_SIZE, "Can't receive packet %d:%s", errno, pcap_strerror(errno));
return -1;
}
buf = handle->buffer;
while (len >= NLMSG_SPACE(0)) {
const struct nlmsghdr *nlh = (const struct nlmsghdr *) buf;
u_int32_t msg_len;
nftype_t type = OTHER;
if (nlh->nlmsg_len < sizeof(struct nlmsghdr) || len < nlh->nlmsg_len) {
snprintf(handle->errbuf, PCAP_ERRBUF_SIZE, "Message truncated: (got: %d) (nlmsg_len: %u)", len, nlh->nlmsg_len);
return -1;
}
if (NFNL_SUBSYS_ID(nlh->nlmsg_type) == NFNL_SUBSYS_ULOG &&
NFNL_MSG_TYPE(nlh->nlmsg_type) == NFULNL_MSG_PACKET)
type = NFLOG;
else if (NFNL_SUBSYS_ID(nlh->nlmsg_type) == NFNL_SUBSYS_QUEUE &&
NFNL_MSG_TYPE(nlh->nlmsg_type) == NFQNL_MSG_PACKET)
type = NFQUEUE;
if (type != OTHER) {
const unsigned char *payload = NULL;
struct pcap_pkthdr pkth;
const struct nfgenmsg *nfg = NULL;
int id = 0;
if (handle->linktype != DLT_NFLOG) {
const struct nfattr *payload_attr = NULL;
if (nlh->nlmsg_len < HDR_LENGTH) {
snprintf(handle->errbuf, PCAP_ERRBUF_SIZE, "Malformed message: (nlmsg_len: %u)", nlh->nlmsg_len);
return -1;
}
nfg = NLMSG_DATA(nlh);
if (nlh->nlmsg_len > HDR_LENGTH) {
struct nfattr *attr = NFM_NFA(nfg);
int attr_len = nlh->nlmsg_len - NLMSG_ALIGN(HDR_LENGTH);
while (NFA_OK(attr, attr_len)) {
if (type == NFQUEUE) {
switch (NFA_TYPE(attr)) {
case NFQA_PACKET_HDR:
{
const struct nfqnl_msg_packet_hdr *pkt_hdr = (const struct nfqnl_msg_packet_hdr *) NFA_DATA(attr);
id = ntohl(pkt_hdr->packet_id);
break;
}
case NFQA_PAYLOAD:
payload_attr = attr;
break;
}
} else if (type == NFLOG) {
switch (NFA_TYPE(attr)) {
case NFULA_PAYLOAD:
payload_attr = attr;
break;
}
}
attr = NFA_NEXT(attr, attr_len);
}
}
if (payload_attr) {
payload = NFA_DATA(payload_attr);
pkth.len = pkth.caplen = NFA_PAYLOAD(payload_attr);
}
} else {
payload = NLMSG_DATA(nlh);
pkth.caplen = pkth.len = nlh->nlmsg_len-NLMSG_ALIGN(sizeof(struct nlmsghdr));
}
if (payload) {
/* pkth.caplen = min (payload_len, handle->snapshot); */
gettimeofday(&pkth.ts, NULL);
if (handle->fcode.bf_insns == NULL ||
bpf_filter(handle->fcode.bf_insns, payload, pkth.len, pkth.caplen))
{
handlep->packets_read++;
callback(user, &pkth, payload);
count++;
}
}
if (type == NFQUEUE) {
/* XXX, possible responses: NF_DROP, NF_ACCEPT, NF_STOLEN, NF_QUEUE, NF_REPEAT, NF_STOP */
/* if type == NFQUEUE, handle->linktype is always != DLT_NFLOG,
so nfg is always initialized to NLMSG_DATA(nlh). */
if (nfg != NULL)
nfqueue_send_verdict(handle, ntohs(nfg->res_id), id, NF_ACCEPT);
}
}
msg_len = NLMSG_ALIGN(nlh->nlmsg_len);
if (msg_len > len)
msg_len = len;
len -= msg_len;
buf += msg_len;
}
return count;
}
static int
netfilter_set_datalink(pcap_t *handle, int dlt)
{
handle->linktype = dlt;
return 0;
}
static int
netfilter_stats_linux(pcap_t *handle, struct pcap_stat *stats)
{
struct pcap_netfilter *handlep = handle->priv;
stats->ps_recv = handlep->packets_read;
stats->ps_drop = 0;
stats->ps_ifdrop = 0;
return 0;
}
static int
netfilter_inject_linux(pcap_t *handle, const void *buf, size_t size)
{
snprintf(handle->errbuf, PCAP_ERRBUF_SIZE, "inject not supported on netfilter devices");
return (-1);
}
struct my_nfattr {
u_int16_t nfa_len;
u_int16_t nfa_type;
void *data;
};
static int
netfilter_send_config_msg(const pcap_t *handle, u_int16_t msg_type, int ack, u_int8_t family, u_int16_t res_id, const struct my_nfattr *mynfa)
{
char buf[1024] __attribute__ ((aligned));
struct nlmsghdr *nlh = (struct nlmsghdr *) buf;
struct nfgenmsg *nfg = (struct nfgenmsg *) (buf + sizeof(struct nlmsghdr));
struct sockaddr_nl snl;
static unsigned int seq_id;
if (!seq_id)
seq_id = time(NULL);
++seq_id;
nlh->nlmsg_len = NLMSG_LENGTH(sizeof(struct nfgenmsg));
nlh->nlmsg_type = msg_type;
nlh->nlmsg_flags = NLM_F_REQUEST | (ack ? NLM_F_ACK : 0);
nlh->nlmsg_pid = 0; /* to kernel */
nlh->nlmsg_seq = seq_id;
nfg->nfgen_family = family;
nfg->version = NFNETLINK_V0;
nfg->res_id = htons(res_id);
if (mynfa) {
struct nfattr *nfa = (struct nfattr *) (buf + NLMSG_ALIGN(nlh->nlmsg_len));
nfa->nfa_type = mynfa->nfa_type;
nfa->nfa_len = NFA_LENGTH(mynfa->nfa_len);
memcpy(NFA_DATA(nfa), mynfa->data, mynfa->nfa_len);
nlh->nlmsg_len = NLMSG_ALIGN(nlh->nlmsg_len) + NFA_ALIGN(nfa->nfa_len);
}
memset(&snl, 0, sizeof(snl));
snl.nl_family = AF_NETLINK;
if (sendto(handle->fd, nlh, nlh->nlmsg_len, 0, (struct sockaddr *) &snl, sizeof(snl)) == -1)
return -1;
if (!ack)
return 0;
/* waiting for reply loop */
do {
socklen_t addrlen = sizeof(snl);
int len;
/* ignore interrupt system call error */
do {
len = recvfrom(handle->fd, buf, sizeof(buf), 0, (struct sockaddr *) &snl, &addrlen);
} while ((len == -1) && (errno == EINTR));
if (len <= 0)
return len;
if (addrlen != sizeof(snl) || snl.nl_family != AF_NETLINK) {
errno = EINVAL;
return -1;
}
nlh = (struct nlmsghdr *) buf;
if (snl.nl_pid != 0 || seq_id != nlh->nlmsg_seq) /* if not from kernel or wrong sequence skip */
continue;
while (len >= NLMSG_SPACE(0) && NLMSG_OK(nlh, len)) {
if (nlh->nlmsg_type == NLMSG_ERROR || (nlh->nlmsg_type == NLMSG_DONE && nlh->nlmsg_flags & NLM_F_MULTI)) {
if (nlh->nlmsg_len < NLMSG_ALIGN(sizeof(struct nlmsgerr))) {
errno = EBADMSG;
return -1;
}
errno = -(*((int *)NLMSG_DATA(nlh)));
return (errno == 0) ? 0 : -1;
}
nlh = NLMSG_NEXT(nlh, len);
}
} while (1);
return -1; /* never here */
}
static int
nflog_send_config_msg(const pcap_t *handle, u_int8_t family, u_int16_t group_id, const struct my_nfattr *mynfa)
{
return netfilter_send_config_msg(handle, (NFNL_SUBSYS_ULOG << 8) | NFULNL_MSG_CONFIG, 1, family, group_id, mynfa);
}
static int
nflog_send_config_cmd(const pcap_t *handle, u_int16_t group_id, u_int8_t cmd, u_int8_t family)
{
struct nfulnl_msg_config_cmd msg;
struct my_nfattr nfa;
msg.command = cmd;
nfa.data = &msg;
nfa.nfa_type = NFULA_CFG_CMD;
nfa.nfa_len = sizeof(msg);
return nflog_send_config_msg(handle, family, group_id, &nfa);
}
static int
nflog_send_config_mode(const pcap_t *handle, u_int16_t group_id, u_int8_t copy_mode, u_int32_t copy_range)
{
struct nfulnl_msg_config_mode msg;
struct my_nfattr nfa;
msg.copy_range = htonl(copy_range);
msg.copy_mode = copy_mode;
nfa.data = &msg;
nfa.nfa_type = NFULA_CFG_MODE;
nfa.nfa_len = sizeof(msg);
return nflog_send_config_msg(handle, AF_UNSPEC, group_id, &nfa);
}
static int
nfqueue_send_verdict(const pcap_t *handle, u_int16_t group_id, u_int32_t id, u_int32_t verdict)
{
struct nfqnl_msg_verdict_hdr msg;
struct my_nfattr nfa;
msg.id = htonl(id);
msg.verdict = htonl(verdict);
nfa.data = &msg;
nfa.nfa_type = NFQA_VERDICT_HDR;
nfa.nfa_len = sizeof(msg);
return netfilter_send_config_msg(handle, (NFNL_SUBSYS_QUEUE << 8) | NFQNL_MSG_VERDICT, 0, AF_UNSPEC, group_id, &nfa);
}
static int
nfqueue_send_config_msg(const pcap_t *handle, u_int8_t family, u_int16_t group_id, const struct my_nfattr *mynfa)
{
return netfilter_send_config_msg(handle, (NFNL_SUBSYS_QUEUE << 8) | NFQNL_MSG_CONFIG, 1, family, group_id, mynfa);
}
static int
nfqueue_send_config_cmd(const pcap_t *handle, u_int16_t group_id, u_int8_t cmd, u_int16_t pf)
{
struct nfqnl_msg_config_cmd msg;
struct my_nfattr nfa;
msg.command = cmd;
msg.pf = htons(pf);
nfa.data = &msg;
nfa.nfa_type = NFQA_CFG_CMD;
nfa.nfa_len = sizeof(msg);
return nfqueue_send_config_msg(handle, AF_UNSPEC, group_id, &nfa);
}
static int
nfqueue_send_config_mode(const pcap_t *handle, u_int16_t group_id, u_int8_t copy_mode, u_int32_t copy_range)
{
struct nfqnl_msg_config_params msg;
struct my_nfattr nfa;
msg.copy_range = htonl(copy_range);
msg.copy_mode = copy_mode;
nfa.data = &msg;
nfa.nfa_type = NFQA_CFG_PARAMS;
nfa.nfa_len = sizeof(msg);
return nfqueue_send_config_msg(handle, AF_UNSPEC, group_id, &nfa);
}
static int
netfilter_activate(pcap_t* handle)
{
const char *dev = handle->opt.source;
unsigned short groups[32];
int group_count = 0;
nftype_t type = OTHER;
int i;
if (strncmp(dev, NFLOG_IFACE, strlen(NFLOG_IFACE)) == 0) {
dev += strlen(NFLOG_IFACE);
type = NFLOG;
} else if (strncmp(dev, NFQUEUE_IFACE, strlen(NFQUEUE_IFACE)) == 0) {
dev += strlen(NFQUEUE_IFACE);
type = NFQUEUE;
}
if (type != OTHER && *dev == ':') {
dev++;
while (*dev) {
long int group_id;
char *end_dev;
if (group_count == 32) {
snprintf(handle->errbuf, PCAP_ERRBUF_SIZE,
"Maximum 32 netfilter groups! dev: %s",
handle->opt.source);
return PCAP_ERROR;
}
group_id = strtol(dev, &end_dev, 0);
if (end_dev != dev) {
if (group_id < 0 || group_id > 65535) {
snprintf(handle->errbuf, PCAP_ERRBUF_SIZE,
"Netfilter group range from 0 to 65535 (got %ld)",
group_id);
return PCAP_ERROR;
}
groups[group_count++] = (unsigned short) group_id;
dev = end_dev;
}
if (*dev != ',')
break;
dev++;
}
}
if (type == OTHER || *dev) {
snprintf(handle->errbuf, PCAP_ERRBUF_SIZE,
"Can't get netfilter group(s) index from %s",
handle->opt.source);
return PCAP_ERROR;
}
/* if no groups, add default: 0 */
if (!group_count) {
groups[0] = 0;
group_count = 1;
}
/* Initialize some components of the pcap structure. */
handle->bufsize = 128 + handle->snapshot;
handle->offset = 0;
handle->read_op = netfilter_read_linux;
handle->inject_op = netfilter_inject_linux;
handle->setfilter_op = install_bpf_program; /* no kernel filtering */
handle->setdirection_op = NULL;
handle->set_datalink_op = netfilter_set_datalink;
handle->getnonblock_op = pcap_getnonblock_fd;
handle->setnonblock_op = pcap_setnonblock_fd;
handle->stats_op = netfilter_stats_linux;
/* Create netlink socket */
handle->fd = socket(AF_NETLINK, SOCK_RAW, NETLINK_NETFILTER);
if (handle->fd < 0) {
snprintf(handle->errbuf, PCAP_ERRBUF_SIZE, "Can't create raw socket %d:%s", errno, pcap_strerror(errno));
return PCAP_ERROR;
}
if (type == NFLOG) {
handle->linktype = DLT_NFLOG;
handle->dlt_list = (u_int *) malloc(sizeof(u_int) * 2);
if (handle->dlt_list != NULL) {
handle->dlt_list[0] = DLT_NFLOG;
handle->dlt_list[1] = DLT_IPV4;
handle->dlt_count = 2;
}
} else
handle->linktype = DLT_IPV4;
handle->buffer = malloc(handle->bufsize);
if (!handle->buffer) {
snprintf(handle->errbuf, PCAP_ERRBUF_SIZE, "Can't allocate dump buffer: %s", pcap_strerror(errno));
goto close_fail;
}
if (type == NFLOG) {
if (nflog_send_config_cmd(handle, 0, NFULNL_CFG_CMD_PF_UNBIND, AF_INET) < 0) {
snprintf(handle->errbuf, PCAP_ERRBUF_SIZE, "NFULNL_CFG_CMD_PF_UNBIND: %s", pcap_strerror(errno));
goto close_fail;
}
if (nflog_send_config_cmd(handle, 0, NFULNL_CFG_CMD_PF_BIND, AF_INET) < 0) {
snprintf(handle->errbuf, PCAP_ERRBUF_SIZE, "NFULNL_CFG_CMD_PF_BIND: %s", pcap_strerror(errno));
goto close_fail;
}
/* Bind socket to the nflog groups */
for (i = 0; i < group_count; i++) {
if (nflog_send_config_cmd(handle, groups[i], NFULNL_CFG_CMD_BIND, AF_UNSPEC) < 0) {
snprintf(handle->errbuf, PCAP_ERRBUF_SIZE, "Can't listen on group group index: %s", pcap_strerror(errno));
goto close_fail;
}
if (nflog_send_config_mode(handle, groups[i], NFULNL_COPY_PACKET, handle->snapshot) < 0) {
snprintf(handle->errbuf, PCAP_ERRBUF_SIZE, "NFULNL_COPY_PACKET: %s", pcap_strerror(errno));
goto close_fail;
}
}
} else {
if (nfqueue_send_config_cmd(handle, 0, NFQNL_CFG_CMD_PF_UNBIND, AF_INET) < 0) {
snprintf(handle->errbuf, PCAP_ERRBUF_SIZE, "NFQNL_CFG_CMD_PF_UNBIND: %s", pcap_strerror(errno));
goto close_fail;
}
if (nfqueue_send_config_cmd(handle, 0, NFQNL_CFG_CMD_PF_BIND, AF_INET) < 0) {
snprintf(handle->errbuf, PCAP_ERRBUF_SIZE, "NFQNL_CFG_CMD_PF_BIND: %s", pcap_strerror(errno));
goto close_fail;
}
/* Bind socket to the nfqueue groups */
for (i = 0; i < group_count; i++) {
if (nfqueue_send_config_cmd(handle, groups[i], NFQNL_CFG_CMD_BIND, AF_UNSPEC) < 0) {
snprintf(handle->errbuf, PCAP_ERRBUF_SIZE, "Can't listen on group group index: %s", pcap_strerror(errno));
goto close_fail;
}
if (nfqueue_send_config_mode(handle, groups[i], NFQNL_COPY_PACKET, handle->snapshot) < 0) {
snprintf(handle->errbuf, PCAP_ERRBUF_SIZE, "NFQNL_COPY_PACKET: %s", pcap_strerror(errno));
goto close_fail;
}
}
}
if (handle->opt.rfmon) {
/*
* Monitor mode doesn't apply to netfilter devices.
*/
pcap_cleanup_live_common(handle);
return PCAP_ERROR_RFMON_NOTSUP;
}
if (handle->opt.buffer_size != 0) {
/*
* Set the socket buffer size to the specified value.
*/
if (setsockopt(handle->fd, SOL_SOCKET, SO_RCVBUF, &handle->opt.buffer_size, sizeof(handle->opt.buffer_size)) == -1) {
snprintf(handle->errbuf, PCAP_ERRBUF_SIZE, "SO_RCVBUF: %s", pcap_strerror(errno));
goto close_fail;
}
}
handle->selectable_fd = handle->fd;
return 0;
close_fail:
pcap_cleanup_live_common(handle);
return PCAP_ERROR;
}
pcap_t *
netfilter_create(const char *device, char *ebuf, int *is_ours)
{
const char *cp;
pcap_t *p;
/* Does this look like an netfilter device? */
cp = strrchr(device, '/');
if (cp == NULL)
cp = device;
/* Does it begin with NFLOG_IFACE or NFQUEUE_IFACE? */
if (strncmp(cp, NFLOG_IFACE, sizeof NFLOG_IFACE - 1) == 0)
cp += sizeof NFLOG_IFACE - 1;
else if (strncmp(cp, NFQUEUE_IFACE, sizeof NFQUEUE_IFACE - 1) == 0)
cp += sizeof NFQUEUE_IFACE - 1;
else {
/* Nope, doesn't begin with NFLOG_IFACE nor NFQUEUE_IFACE */
*is_ours = 0;
return NULL;
}
/*
* Yes - is that either the end of the name, or is it followed
* by a colon?
*/
if (*cp != ':' && *cp != '\0') {
/* Nope */
*is_ours = 0;
return NULL;
}
/* OK, it's probably ours. */
*is_ours = 1;
p = pcap_create_common(device, ebuf, sizeof (struct pcap_netfilter));
if (p == NULL)
return (NULL);
p->activate_op = netfilter_activate;
return (p);
}
int
netfilter_findalldevs(pcap_if_t **alldevsp, char *err_str)
{
int sock;
sock = socket(AF_NETLINK, SOCK_RAW, NETLINK_NETFILTER);
if (sock < 0) {
/* if netlink is not supported this is not fatal */
if (errno == EAFNOSUPPORT || errno == EPROTONOSUPPORT)
return 0;
snprintf(err_str, PCAP_ERRBUF_SIZE, "Can't open netlink socket %d:%s",
errno, pcap_strerror(errno));
return -1;
}
close(sock);
if (pcap_add_if(alldevsp, NFLOG_IFACE, 0, "Linux netfilter log (NFLOG) interface", err_str) < 0)
return -1;
if (pcap_add_if(alldevsp, NFQUEUE_IFACE, 0, "Linux netfilter queue (NFQUEUE) interface", err_str) < 0)
return -1;
return 0;
}