This functions can be used to convert a vlan interface into the real one and to extract the vlan identifier.
Signed-off-by: Antonio Quartulli antonio@meshcoding.com --- functions.c | 165 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ functions.h | 1 + 2 files changed, 166 insertions(+)
diff --git a/functions.c b/functions.c index 50bb834..fdae6fa 100644 --- a/functions.c +++ b/functions.c @@ -40,6 +40,7 @@ #include <linux/neighbour.h> #include <sys/uio.h> #include <errno.h> +#include <net/if.h>
#include "main.h" #include "functions.h" @@ -764,3 +765,167 @@ struct ether_addr *resolve_mac(const char *asc) out: return mac_result; } + +/** + * vlan_get_link_parse - parse a get_link rtnl message and extract the important + * data + * @nh: the reply header + * @iface: pointer to the buffer where the link interface has to be stored (it + * is allocated by this function) + * + * Return the vid in case of success or -1 otherwise + */ +static int vlan_get_link_parse(struct nlmsghdr *nh, char **iface) +{ + struct ifinfomsg *ifi = NLMSG_DATA(nh); + size_t vlan_len, info_len, len = nh->nlmsg_len; + struct rtattr *rta, *info, *vlan; + int idx = -1, vid = -1; + + *iface = NULL; + + rta = IFLA_RTA(ifi); + while (RTA_OK(rta, len)) { + /* check if the interface is a vlan */ + if (rta->rta_type == IFLA_LINKINFO) { + info = RTA_DATA(rta); + info_len = RTA_PAYLOAD(rta); + + while (RTA_OK(info, info_len)) { + if (info->rta_type == IFLA_INFO_KIND && + strcmp(RTA_DATA(info), "vlan")) + goto err; + + if (info->rta_type == IFLA_INFO_DATA) { + vlan = RTA_DATA(info); + vlan_len = RTA_PAYLOAD(info); + + while (RTA_OK(vlan, vlan_len)) { + if (vlan->rta_type == IFLA_VLAN_ID) + vid = *(int *)RTA_DATA(vlan); + vlan = RTA_NEXT(vlan, vlan_len); + } + } + info = RTA_NEXT(info, info_len); + } + } + + /* extract the name of the "link" interface */ + if (rta->rta_type == IFLA_LINK) { + idx = *(int *)RTA_DATA(rta); + + *iface = malloc(IFNAMSIZ + 1); + if (!if_indextoname(idx, *iface)) + goto err; + } + rta = RTA_NEXT(rta, len); + } + + if (vid == -1) + goto err; + + if (idx <= 0) + goto err; + + return vid; +err: + free(*iface); + return -1; +} + +/** + * vlan_get_link_dump - receive and dump a get_link rtnl reply + * @sock: the socket to listen for the reply on + * @buf: buffer where the reply has to be dumped to + * @buflen: length of the buffer + * + * Returns the amount of dumped bytes + */ +static ssize_t vlan_get_link_dump(int sock, void *buf, size_t buflen) +{ + struct sockaddr_nl nladdr; + struct msghdr msg; + struct iovec iov; + + memset(&msg, 0, sizeof(msg)); + memset(&iov, 0, sizeof(iov)); + + msg.msg_iov = &iov; + msg.msg_iovlen = 1; + msg.msg_controllen = 0; + msg.msg_control = NULL; + msg.msg_flags = 0; + msg.msg_name = &nladdr; + msg.msg_namelen = sizeof(nladdr); + + iov.iov_len = buflen; + iov.iov_base = buf; + + return recvmsg(sock, &msg, 0); +} + +/** + * vlan_get_link_open - send a get_link request + * @ifname: the interface to query + * + * Returns 0 in case of success or a negative error code otherwise + */ +static int vlan_get_link_open(const char *ifname) +{ + struct { + struct nlmsghdr hdr; + struct ifinfomsg ifi; + /* attribute has to be NLMSG aligned */ + struct rtattr rta_ifname __attribute__ ((aligned(NLMSG_ALIGNTO))); + char ifname[IFNAMSIZ + 1]; + } nlreq; + + memset(&nlreq, 0, sizeof(nlreq)); + nlreq.hdr.nlmsg_len = sizeof(nlreq); + nlreq.hdr.nlmsg_type = RTM_GETLINK; + nlreq.hdr.nlmsg_flags = NLM_F_REQUEST; + nlreq.ifi.ifi_family = AF_UNSPEC; + + nlreq.rta_ifname.rta_type = IFLA_IFNAME; + nlreq.rta_ifname.rta_len = IFNAMSIZ + 1; + strncpy(nlreq.ifname, ifname, IFNAMSIZ); + + return rtnl_open(&nlreq.hdr, 0); +} + +/** + * vlan_get_link - convert a VLAN interface into its parent one + * @ifname: the interface to convert + * @parent: buffer where the parent interface name will be written (allocated by + * this function) + * + * Returns the vlan identifier on success or -1 on error + */ +int vlan_get_link(const char *ifname, char **parent) +{ + int vid = -1, socknl; + void *buf = NULL; + size_t buflen; + ssize_t len; + + buflen = 8192; + buf = malloc(buflen); + if (!buf) + goto err; + + socknl = vlan_get_link_open(ifname); + if (socknl < 0) + goto err; + + len = vlan_get_link_dump(socknl, buf, buflen); + if (len < 0) + goto err_sock; + + vid = vlan_get_link_parse(buf, parent); + +err_sock: + close(socknl); +err: + free(buf); + return vid; +} diff --git a/functions.h b/functions.h index 522c607..14ba525 100644 --- a/functions.h +++ b/functions.h @@ -42,6 +42,7 @@ int write_file(const char *dir, const char *fname, const char *arg1, const char *arg2); struct ether_addr *translate_mac(char *mesh_iface, struct ether_addr *mac); struct ether_addr *resolve_mac(const char *asc); +int vlan_get_link(const char *ifname, char **parent);
extern char *line_ptr;