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Use netlink when setting the link MTU.

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This commit is contained in:
Nicholas J. Kain 2014-03-16 18:07:09 -04:00
parent 987bffe157
commit 9de62e7b75
1 changed files with 63 additions and 18 deletions
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81
ndhc/ifset.c
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@ -30,6 +30,7 @@
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <limits.h>
#define __USE_GNU 1
#include <sys/socket.h>
#include <sys/un.h>
@ -161,6 +162,35 @@ static ssize_t rtnl_if_flags_send(int fd, int type, int ifi_flags)
return rtnl_do_send(fd, request, header->nlmsg_len, __func__);
}
static ssize_t rtnl_if_mtu_set(int fd, unsigned int mtu)
{
uint8_t request[NLMSG_ALIGN(sizeof(struct nlmsghdr)) +
NLMSG_ALIGN(sizeof(struct ifinfomsg)) +
RTA_LENGTH(sizeof(uint32_t))];
struct nlmsghdr *header;
struct ifinfomsg *ifinfomsg;
memset(&request, 0, sizeof request);
header = (struct nlmsghdr *)request;
header->nlmsg_len = NLMSG_LENGTH(sizeof(struct ifinfomsg));
header->nlmsg_type = RTM_SETLINK;
header->nlmsg_flags = NLM_F_REPLACE | NLM_F_ACK | NLM_F_REQUEST;
header->nlmsg_seq = ifset_nl_seq++;
ifinfomsg = NLMSG_DATA(header);
ifinfomsg->ifi_index = client_config.ifindex;
ifinfomsg->ifi_change = 0xffffffff;
if (nl_add_rtattr(header, sizeof request, IFLA_MTU,
&mtu, sizeof mtu) < 0) {
log_line("%s: (%s) couldn't add IFLA_MTU to nlmsg",
client_config.interface, __func__);
return -1;
}
return rtnl_do_send(fd, request, header->nlmsg_len, __func__);
}
static ssize_t rtnl_addr_broadcast_send(int fd, int type, int ifa_flags,
int ifa_scope, uint32_t *ipaddr,
uint32_t *bcast, uint8_t prefixlen)
@ -497,31 +527,46 @@ void perform_router(const char *str, size_t len)
void perform_mtu(const char *str, size_t len)
{
int fd;
unsigned int mtu;
struct ifreq ifrt;
if (!str)
return;
if (len < 2)
return;
mtu = strtol(str, NULL, 10);
// Minimum MTU for physical IPv4 links is 576 octets.
if (mtu < 576)
return;
ifrt.ifr_mtu = mtu;
strnkcpy(ifrt.ifr_name, client_config.interface, IFNAMSIZ);
fd = socket(AF_INET, SOCK_DGRAM, 0);
if (fd == -1) {
log_line("%s: (perform_mtu) failed to open interface socket: %s",
client_config.interface, strerror(errno));
char *estr;
long tmtu = strtol(str, &estr, 10);
if (estr == str) {
log_line("%s: (%s) provided mtu arg isn't a valid number",
client_config.interface, __func__);
return;
}
if (ioctl(fd, SIOCSIFMTU, &ifrt) < 0)
log_line("%s: failed to set MTU (%d): %s", client_config.interface, mtu,
strerror(errno));
if ((tmtu == LONG_MAX || tmtu == LONG_MIN) && errno == ERANGE) {
log_line("%s: (%s) provided mtu arg would overflow a long",
client_config.interface, __func__);
return;
}
if (tmtu > UINT_MAX) {
log_line("%s: (%s) provided mtu arg would overflow unsigned int",
client_config.interface, __func__);
return;
}
// 68 bytes for IPv4. 1280 bytes for IPv6.
if (tmtu < 68) {
log_line("%s: (%s) provided mtu arg (%ul) less than minimum MTU (68)",
client_config.interface, __func__, tmtu);
return;
}
unsigned int mtu = (unsigned int)tmtu;
int fd = socket(AF_NETLINK, SOCK_DGRAM, NETLINK_ROUTE);
if (fd < 0) {
log_line("%s: (%s) netlink socket open failed: %s",
client_config.interface, __func__, strerror(errno));
return;
}
if (rtnl_if_mtu_set(fd, mtu) < 0)
log_line("%s: (%s) failed to set MTU [%d]",
client_config.interface, __func__, mtu);
else
log_line("MTU set to: '%s'", str);
close(fd);