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// SPDX-License-Identifier: GPL-2.0-or-later
/*
* VRRP ARP handling.
* Copyright (C) 2001-2017 Alexandre Cassen
* Portions:
* Copyright (C) 2018-2019 Cumulus Networks, Inc.
* Quentin Young
*/
#include <zebra.h>
#include <linux/if_packet.h>
#include <net/if_arp.h>
#include <netinet/if_ether.h>
#include "lib/if.h"
#include "lib/linklist.h"
#include "lib/log.h"
#include "lib/memory.h"
#include "lib/prefix.h"
#include "vrrp.h"
#include "vrrp_arp.h"
#include "vrrp_debug.h"
#define VRRP_LOGPFX "[ARP] "
/*
* The size of the garp packet buffer should be the large enough to hold the
* largest arp packet to be sent + the size of the link layer header for the
* corresponding protocol. In this case we hardcode for Ethernet.
*/
#define GARP_BUFFER_SIZE \
sizeof(struct ether_header) + sizeof(struct arphdr) + 2 * ETH_ALEN \
+ 2 * sizeof(struct in_addr)
/* static vars */
static int garp_fd = -1;
/* Send the gratuitous ARP message */
static ssize_t vrrp_send_garp(struct interface *ifp, uint8_t *buf,
ssize_t pack_len)
{
struct sockaddr_ll sll;
ssize_t len;
/* Build the dst device */
memset(&sll, 0, sizeof(sll));
sll.sll_family = AF_PACKET;
sll.sll_protocol = ETH_P_ARP;
sll.sll_ifindex = (int)ifp->ifindex;
sll.sll_halen = ifp->hw_addr_len;
memset(sll.sll_addr, 0xFF, ETH_ALEN);
/* Send packet */
len = sendto(garp_fd, buf, pack_len, 0, (struct sockaddr *)&sll,
sizeof(sll));
return len;
}
/* Build a gratuitous ARP message over a specific interface */
static ssize_t vrrp_build_garp(uint8_t *buf, struct interface *ifp,
struct in_addr *v4)
{
uint8_t *arp_ptr;
if (ifp->hw_addr_len == 0)
return -1;
/* Build Ethernet header */
struct ether_header *eth = (struct ether_header *)buf;
memset(eth->ether_dhost, 0xFF, ETH_ALEN);
memcpy(eth->ether_shost, ifp->hw_addr, ETH_ALEN);
eth->ether_type = htons(ETHERTYPE_ARP);
/* Build ARP payload */
struct arphdr *arph = (struct arphdr *)(buf + ETHER_HDR_LEN);
arph->ar_hrd = htons(HWTYPE_ETHER);
arph->ar_pro = htons(ETHERTYPE_IP);
arph->ar_hln = ifp->hw_addr_len;
arph->ar_pln = sizeof(struct in_addr);
arph->ar_op = htons(ARPOP_REQUEST);
arp_ptr = (uint8_t *)(arph + 1);
/* Source MAC: us */
memcpy(arp_ptr, ifp->hw_addr, ifp->hw_addr_len);
arp_ptr += ifp->hw_addr_len;
/* Source IP: us */
memcpy(arp_ptr, v4, sizeof(struct in_addr));
arp_ptr += sizeof(struct in_addr);
/* Dest MAC: broadcast */
memset(arp_ptr, 0xFF, ETH_ALEN);
arp_ptr += ifp->hw_addr_len;
/* Dest IP: us */
memcpy(arp_ptr, v4, sizeof(struct in_addr));
arp_ptr += sizeof(struct in_addr);
return arp_ptr - buf;
}
void vrrp_garp_send(struct vrrp_router *r, struct in_addr *v4)
{
struct interface *ifp = r->mvl_ifp;
uint8_t garpbuf[GARP_BUFFER_SIZE];
ssize_t garpbuf_len;
ssize_t sent_len;
char astr[INET_ADDRSTRLEN];
/* If the interface doesn't support ARP, don't try sending */
if (ifp->flags & IFF_NOARP) {
zlog_warn(
VRRP_LOGPFX VRRP_LOGPFX_VRID VRRP_LOGPFX_FAM
"Unable to send gratuitous ARP on %s; has IFF_NOARP",
r->vr->vrid, family2str(r->family), ifp->name);
return;
}
/* Build garp */
garpbuf_len = vrrp_build_garp(garpbuf, ifp, v4);
if (garpbuf_len < 0) {
zlog_warn(
VRRP_LOGPFX VRRP_LOGPFX_VRID VRRP_LOGPFX_FAM
"Unable to send gratuitous ARP on %s; MAC address unknown",
r->vr->vrid, family2str(r->family), ifp->name);
return;
};
/* Send garp */
inet_ntop(AF_INET, v4, astr, sizeof(astr));
DEBUGD(&vrrp_dbg_arp,
VRRP_LOGPFX VRRP_LOGPFX_VRID VRRP_LOGPFX_FAM
"Sending gratuitous ARP on %s for %s",
r->vr->vrid, family2str(r->family), ifp->name, astr);
if (DEBUG_MODE_CHECK(&vrrp_dbg_arp, DEBUG_MODE_ALL))
zlog_hexdump(garpbuf, garpbuf_len);
sent_len = vrrp_send_garp(ifp, garpbuf, garpbuf_len);
if (sent_len < 0)
zlog_warn(VRRP_LOGPFX VRRP_LOGPFX_VRID VRRP_LOGPFX_FAM
"Error sending gratuitous ARP on %s for %s",
r->vr->vrid, family2str(r->family), ifp->name, astr);
else
++r->stats.garp_tx_cnt;
}
void vrrp_garp_send_all(struct vrrp_router *r)
{
assert(r->family == AF_INET);
struct interface *ifp = r->mvl_ifp;
/* If the interface doesn't support ARP, don't try sending */
if (ifp->flags & IFF_NOARP) {
zlog_warn(
VRRP_LOGPFX VRRP_LOGPFX_VRID VRRP_LOGPFX_FAM
"Unable to send gratuitous ARP on %s; has IFF_NOARP",
r->vr->vrid, family2str(r->family), ifp->name);
return;
}
struct listnode *ln;
struct ipaddr *ip;
for (ALL_LIST_ELEMENTS_RO(r->addrs, ln, ip))
vrrp_garp_send(r, &ip->ipaddr_v4);
}
void vrrp_garp_init(void)
{
/* Create the socket descriptor */
/* FIXME: why ETH_P_RARP? */
errno = 0;
frr_with_privs(&vrrp_privs) {
garp_fd = socket(PF_PACKET, SOCK_RAW | SOCK_CLOEXEC,
htons(ETH_P_RARP));
}
if (garp_fd > 0) {
DEBUGD(&vrrp_dbg_sock,
VRRP_LOGPFX "Initialized gratuitous ARP socket");
DEBUGD(&vrrp_dbg_arp,
VRRP_LOGPFX "Initialized gratuitous ARP subsystem");
} else {
zlog_err(VRRP_LOGPFX
"Error initializing gratuitous ARP subsystem");
}
}
void vrrp_garp_fini(void)
{
close(garp_fd);
garp_fd = -1;
DEBUGD(&vrrp_dbg_arp,
VRRP_LOGPFX "Deinitialized gratuitous ARP subsystem");
}
bool vrrp_garp_is_init(void)
{
return garp_fd > 0;
}
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