l2_packet_pcap.c

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#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#ifndef CONFIG_NATIVE_WINDOWS
#include <sys/ioctl.h>
#endif /* CONFIG_NATIVE_WINDOWS */
#include <errno.h>
#include <pcap.h>
#ifndef CONFIG_WINPCAP
#include <dnet.h>
#endif /* CONFIG_WINPCAP */
#if defined(__linux__) || defined(__CYGWIN__)
#include <arpa/inet.h>
#include <sys/socket.h>
#endif /* __linux__ || __CYGWIN__ */

#include "common.h"
#include "eloop.h"
#include "l2_packet.h"


static const u8 pae_group_addr[ETH_ALEN] =
{ 0x01, 0x80, 0xc2, 0x00, 0x00, 0x03 };

struct l2_packet_data {
        pcap_t *pcap;
#ifdef CONFIG_WINPCAP
        unsigned int num_fast_poll;
#else /* CONFIG_WINPCAP */
        eth_t *eth;
#endif /* CONFIG_WINPCAP */
        char ifname[100];
        u8 own_addr[ETH_ALEN];
        void (*rx_callback)(void *ctx, const u8 *src_addr,
                            const u8 *buf, size_t len);
        void *rx_callback_ctx;
        int l2_hdr; /* whether to include layer 2 (Ethernet) header in calls
                        * to rx_callback */
};


int l2_packet_get_own_addr(struct l2_packet_data *l2, u8 *addr)
{
        memcpy(addr, l2->own_addr, ETH_ALEN);
        return 0;
}


#ifndef CONFIG_WINPCAP
static int l2_packet_init_libdnet(struct l2_packet_data *l2)
{
        eth_addr_t own_addr;

        l2->eth = eth_open(l2->ifname);
        if (!l2->eth) {
                printf("Failed to open interface '%s'.\n", l2->ifname);
                perror("eth_open");
                return -1;
        }

        if (eth_get(l2->eth, &own_addr) < 0) {
                printf("Failed to get own hw address from interface '%s'.\n",
                       l2->ifname);
                perror("eth_get");
                eth_close(l2->eth);
                l2->eth = NULL;
                return -1;
        }
        memcpy(l2->own_addr, own_addr.data, ETH_ALEN);

        return 0;
}
#endif /* CONFIG_WINPCAP */


int l2_packet_send(struct l2_packet_data *l2, const u8 *dst_addr, u16 proto,
                   const u8 *buf, size_t len)
{
        int ret;
        struct l2_ethhdr *eth;

        if (l2 == NULL)
                return -1;

        if (l2->l2_hdr) {
#ifdef CONFIG_WINPCAP
                ret = pcap_sendpacket(l2->pcap, buf, len);
#else /* CONFIG_WINPCAP */
                ret = eth_send(l2->eth, buf, len);
#endif /* CONFIG_WINPCAP */
        } else {
                size_t mlen = sizeof(*eth) + len;
                eth = malloc(mlen);
                if (eth == NULL)
                        return -1;

                memcpy(eth->h_dest, dst_addr, ETH_ALEN);
                memcpy(eth->h_source, l2->own_addr, ETH_ALEN);
                eth->h_proto = htons(proto);
                memcpy(eth + 1, buf, len);

#ifdef CONFIG_WINPCAP
                ret = pcap_sendpacket(l2->pcap, (u8 *) eth, mlen);
#else /* CONFIG_WINPCAP */
                ret = eth_send(l2->eth, (u8 *) eth, mlen);
#endif /* CONFIG_WINPCAP */

                free(eth);
        }

        return ret;
}


#ifndef CONFIG_WINPCAP
static void l2_packet_receive(int sock, void *eloop_ctx, void *sock_ctx)
{
        struct l2_packet_data *l2 = eloop_ctx;
        pcap_t *pcap = sock_ctx;
        struct pcap_pkthdr hdr;
        const u_char *packet;
        struct l2_ethhdr *ethhdr;
        unsigned char *buf;
        size_t len;

        packet = pcap_next(pcap, &hdr);

        if (packet == NULL || hdr.caplen < sizeof(*ethhdr))
                return;

        ethhdr = (struct l2_ethhdr *) packet;
        if (l2->l2_hdr) {
                buf = (unsigned char *) ethhdr;
                len = hdr.caplen;
        } else {
                buf = (unsigned char *) (ethhdr + 1);
                len = hdr.caplen - sizeof(*ethhdr);
        }
        l2->rx_callback(l2->rx_callback_ctx, ethhdr->h_source, buf, len);
}
#endif /* CONFIG_WINPCAP */


#ifdef CONFIG_WINPCAP
static void l2_packet_receive_cb(u_char *user, const struct pcap_pkthdr *hdr,
                                 const u_char *pkt_data)
{
        struct l2_packet_data *l2 = (struct l2_packet_data *) user;
        struct l2_ethhdr *ethhdr;
        unsigned char *buf;
        size_t len;

        if (pkt_data == NULL || hdr->caplen < sizeof(*ethhdr))
                return;

        ethhdr = (struct l2_ethhdr *) pkt_data;
        if (l2->l2_hdr) {
                buf = (unsigned char *) ethhdr;
                len = hdr->caplen;
        } else {
                buf = (unsigned char *) (ethhdr + 1);
                len = hdr->caplen - sizeof(*ethhdr);
        }
        l2->rx_callback(l2->rx_callback_ctx, ethhdr->h_source, buf, len);
        /*
         * Use shorter poll interval for 3 seconds to reduce latency during key
         * handshake.
         */
        l2->num_fast_poll = 3 * 50;
}


static void l2_packet_receive_timeout(void *eloop_ctx, void *timeout_ctx)
{
        struct l2_packet_data *l2 = eloop_ctx;
        pcap_t *pcap = timeout_ctx;
        int timeout;

        if (l2->num_fast_poll > 0) {
                timeout = 20000;
                l2->num_fast_poll--;
        } else
                timeout = 100000;

        /* Register new timeout before calling l2_packet_receive() since
         * receive handler may free this l2_packet instance (which will
         * cancel this timeout). */
        eloop_register_timeout(0, timeout, l2_packet_receive_timeout,
                               l2, pcap);
        pcap_dispatch(pcap, 10, l2_packet_receive_cb, (u_char *) l2);
}
#endif /* CONFIG_WINPCAP */


static int l2_packet_init_libpcap(struct l2_packet_data *l2,
                                  unsigned short protocol)
{
        bpf_u_int32 pcap_maskp, pcap_netp;
        char pcap_filter[200], pcap_err[PCAP_ERRBUF_SIZE];
        struct bpf_program pcap_fp;

        pcap_lookupnet(l2->ifname, &pcap_netp, &pcap_maskp, pcap_err);
        l2->pcap = pcap_open_live(l2->ifname, 2500, 0, 10, pcap_err);
        if (l2->pcap == NULL) {
                fprintf(stderr, "pcap_open_live: %s\n", pcap_err);
                fprintf(stderr, "ifname='%s'\n", l2->ifname);
                return -1;
        }
#ifdef CONFIG_WINPCAP
        if (pcap_setnonblock(l2->pcap, 1, pcap_err) < 0)
                fprintf(stderr, "pcap_setnonblock: %s\n",
                        pcap_geterr(l2->pcap));
#else /* CONFIG_WINPCAP */
        if (pcap_datalink(l2->pcap) != DLT_EN10MB &&
            pcap_set_datalink(l2->pcap, DLT_EN10MB) < 0) {
                fprintf(stderr, "pcap_set_datalinke(DLT_EN10MB): %s\n",
                        pcap_geterr(l2->pcap));
                return -1;
        }
#endif /* CONFIG_WINPCAP */
        snprintf(pcap_filter, sizeof(pcap_filter),
                 "not ether src " MACSTR " and "
                 "( ether dst " MACSTR " or ether dst " MACSTR " ) and "
                 "ether proto 0x%x",
                 MAC2STR(l2->own_addr), /* do not receive own packets */
                 MAC2STR(l2->own_addr), MAC2STR(pae_group_addr),
                 protocol);
        if (pcap_compile(l2->pcap, &pcap_fp, pcap_filter, 1, pcap_netp) < 0) {
                fprintf(stderr, "pcap_compile: %s\n", pcap_geterr(l2->pcap));
                return -1;
        }

        if (pcap_setfilter(l2->pcap, &pcap_fp) < 0) {
                fprintf(stderr, "pcap_setfilter: %s\n", pcap_geterr(l2->pcap));
                return -1;
        }

        pcap_freecode(&pcap_fp);
#ifdef BIOCIMMEDIATE
        /*
         * When libpcap uses BPF we must enable "immediate mode" to
         * receive frames right away; otherwise the system may
         * buffer them for us.
         */
        {
                unsigned int on = 1;
                if (ioctl(pcap_fileno(l2->pcap), BIOCIMMEDIATE, &on) < 0) {
                        fprintf(stderr, "%s: cannot enable immediate mode on "
                                "interface %s: %s\n",
                                __func__, l2->ifname, strerror(errno));
                        /* XXX should we fail? */
                }
        }
#endif /* BIOCIMMEDIATE */

#ifdef CONFIG_WINPCAP
        eloop_register_timeout(0, 100000, l2_packet_receive_timeout,
                               l2, l2->pcap);
#else /* CONFIG_WINPCAP */
        eloop_register_read_sock(pcap_get_selectable_fd(l2->pcap),
                                 l2_packet_receive, l2, l2->pcap);
#endif /* CONFIG_WINPCAP */

        return 0;
}


struct l2_packet_data * l2_packet_init(
        const char *ifname, const u8 *own_addr, unsigned short protocol,
        void (*rx_callback)(void *ctx, const u8 *src_addr,
                            const u8 *buf, size_t len),
        void *rx_callback_ctx, int l2_hdr)
{
        struct l2_packet_data *l2;

        l2 = malloc(sizeof(struct l2_packet_data));
        if (l2 == NULL)
                return NULL;
        memset(l2, 0, sizeof(*l2));
        strncpy(l2->ifname, ifname, sizeof(l2->ifname));
        l2->rx_callback = rx_callback;
        l2->rx_callback_ctx = rx_callback_ctx;
        l2->l2_hdr = l2_hdr;

#ifdef CONFIG_WINPCAP
        if (own_addr)
                memcpy(l2->own_addr, own_addr, ETH_ALEN);
#else /* CONFIG_WINPCAP */
        if (l2_packet_init_libdnet(l2))
                return NULL;
#endif /* CONFIG_WINPCAP */

        if (l2_packet_init_libpcap(l2, protocol)) {
#ifndef CONFIG_WINPCAP
                eth_close(l2->eth);
#endif /* CONFIG_WINPCAP */
                free(l2);
                return NULL;
        }

        return l2;
}


void l2_packet_deinit(struct l2_packet_data *l2)
{
        if (l2 == NULL)
                return;

#ifdef CONFIG_WINPCAP
        eloop_cancel_timeout(l2_packet_receive_timeout, l2, l2->pcap);
#else /* CONFIG_WINPCAP */
        if (l2->eth)
                eth_close(l2->eth);
        eloop_unregister_read_sock(pcap_get_selectable_fd(l2->pcap));
#endif /* CONFIG_WINPCAP */
        if (l2->pcap)
                pcap_close(l2->pcap);
        free(l2);
}


int l2_packet_get_ip_addr(struct l2_packet_data *l2, char *buf, size_t len)
{
        pcap_if_t *devs, *dev;
        struct pcap_addr *addr;
        struct sockaddr_in *saddr;
        int found = 0;
        char err[PCAP_ERRBUF_SIZE + 1];

        if (pcap_findalldevs(&devs, err) < 0) {
                wpa_printf(MSG_DEBUG, "pcap_findalldevs: %s\n", err);
                return -1;
        }

        for (dev = devs; dev && !found; dev = dev->next) {
                if (strcmp(dev->name, l2->ifname) != 0)
                        continue;

                addr = dev->addresses;
                while (addr) {
                        saddr = (struct sockaddr_in *) addr->addr;
                        if (saddr && saddr->sin_family == AF_INET) {
                                snprintf(buf, len, "%s",
                                         inet_ntoa(saddr->sin_addr));
                                found = 1;
                                break;
                        }
                        addr = addr->next;
                }
        }

        pcap_freealldevs(devs);

        return found ? 0 : -1;
}


void l2_packet_notify_auth_start(struct l2_packet_data *l2)
{
#ifdef CONFIG_WINPCAP
        /*
         * Use shorter poll interval for 3 seconds to reduce latency during key
         * handshake.
         */
        l2->num_fast_poll = 3 * 50;
        eloop_cancel_timeout(l2_packet_receive_timeout, l2, l2->pcap);
        eloop_register_timeout(0, 10000, l2_packet_receive_timeout,
                               l2, l2->pcap);
#endif /* CONFIG_WINPCAP */
}

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