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Separate change_interface_state() into get/set_if_flags()

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For configuring a TAP interface, we need to set different options, which
is not easily feasible with the current change_interface_state() API (or
would make it more complex). To simplify while allowing to set flags
more flexibly, separate into two functions get/set_if_flags().
This commit is contained in:
Robert Schmidt
2026-01-20 11:11:28 +01:00
parent 42fd19dc5c
commit e9ac0c70c8
1 changed files with 39 additions and 31 deletions
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common/utils/tun_if.c
+39 -31
View File
@@ -158,42 +158,47 @@ static bool setInterfaceParameter(int sock_fd, const char *ifn, int af, const ch
}
typedef enum { INTERFACE_DOWN, INTERFACE_UP } if_action_t;
/*
* \brief bring interface up (up != 0) or down (up == 0)
* \brief Get an interface's flags.
* \param[in] sock_fd socket to use for getting the flags
* \param[in] ifn the interface name for which to get flags
* \param[out] flags the flags of the interface
* \return true on success, false otherwise
*/
static bool change_interface_state(int sock_fd, const char *ifn, if_action_t if_action)
static bool get_if_flags(int sock_fd, const char *ifn, short *flags)
{
const char *action = if_action == INTERFACE_DOWN ? "DOWN" : "UP";
struct ifreq ifr = {0};
strncpy(ifr.ifr_name, ifn, sizeof(ifr.ifr_name) - 1);
/* get flags of this interface: see netdevice(7) */
bool success = ioctl(sock_fd, SIOCGIFFLAGS, (caddr_t)&ifr) == 0;
if (!success && if_action == INTERFACE_DOWN && errno == ENODEV) {
LOG_W(OIP, "trying to remove non-existant device %s\n", ifn);
return true;
int success = ioctl(sock_fd, SIOCGIFFLAGS, (caddr_t)&ifr) == 0;
if (!success) {
LOG_W(OIP, "On interface %s: ioctl() failed: %d, %s\n", ifn, errno, strerror(errno));
return false;
}
LOG_D(OIP, "Got flags for %s: 0x%x (action: %s)\n", ifn, ifr.ifr_flags, action);
if (if_action == INTERFACE_UP) {
ifr.ifr_flags |= IFF_UP | IFF_NOARP | IFF_POINTOPOINT;
ifr.ifr_flags &= ~IFF_MULTICAST;
} else {
ifr.ifr_flags &= ~IFF_UP;
}
success = ioctl(sock_fd, SIOCSIFFLAGS, (caddr_t)&ifr) == 0;
if (!success)
goto fail_interface_state;
LOG_D(OIP, "Interface %s successfully set %s\n", ifn, action);
*flags = ifr.ifr_flags;
return true;
}
fail_interface_state:
LOG_E(OIP, "Bringing interface %s for %s: ioctl call failed: %d, %s\n", action, ifn, errno, strerror(errno));
return false;
/*
* \brief Set an interface's flags.
* \param[in] sock_fd socket to use for setting the flags
* \param[in] ifn the interface name for which to set flags
* \param[in] flags the flags to set for the interface
* \return true on success, false otherwise
*/
static bool set_if_flags(int sock_fd, const char *ifn, short flags)
{
struct ifreq ifr = {0};
strncpy(ifr.ifr_name, ifn, sizeof(ifr.ifr_name) - 1);
ifr.ifr_flags = flags;
int success = ioctl(sock_fd, SIOCSIFFLAGS, (caddr_t)&ifr) == 0;
if (!success) {
LOG_W(OIP, "On interface %s: ioctl() failed: %d, %s\n", ifn, errno, strerror(errno));
return false;
}
return true;
}
@@ -227,8 +232,10 @@ bool tun_config(const char* ifname, const char *ipv4, const char *ipv6)
close(sock_fd);
}
// if successfully set IP addresses: set iterface up, disable ARP, no
// multicast, point-to-point
if (success)
success = change_interface_state(sock_fd, ifname, INTERFACE_UP);
success = set_if_flags(sock_fd, ifname, (IFF_UP | IFF_NOARP | IFF_POINTOPOINT) & ~IFF_MULTICAST);
if (success)
LOG_I(OIP, "Interface %s successfully configured, IPv4 %s, IPv6 %s\n", ifname, ipv4, ipv6);
@@ -283,11 +290,12 @@ void tun_destroy(const char *dev)
return;
}
bool success = change_interface_state(fd, dev, INTERFACE_DOWN);
// interface not up => down
short flags;
bool success = get_if_flags(fd, dev, &flags);
success = success && set_if_flags(fd, dev, flags & ~IFF_UP);
if (success) {
LOG_I(UTIL, "Interface %s is now down.\n", dev);
} else {
LOG_E(UTIL, "Could not bring interface %s down.\n", dev);
}
} // no else: get_if_flags()/set_if_flags() should have printed error
close(fd);
}