How net-based IOCTL calls are made – prerequisite for other wiki pages.
UAPI links:
Kernel links:
struct file_operations socket_file_ops
)Git repo is here.
From ethtool.c
, a simple wrapper around the ioctl()
call:
#ifndef TEST_ETHTOOL int send_ioctl(struct cmd_context *ctx, void *cmd) { ctx->ifr.ifr_data = cmd; // command-specific structure return ioctl(ctx->fd, SIOCETHTOOL, &ctx->ifr); } #endif
QUESTION: What is returned in ifreq->cmd?
From internal.h
, struct cmd_context
showing the embedded struct ifreq
:
/* Context for sub-commands */ struct cmd_context { const char *devname; /* net device name */ int fd; /* socket suitable for ethtool ioctl */ struct ifreq ifr; /* ifreq suitable for ethtool ioctl */ int argc; /* number of arguments to the sub-command */ char **argp; /* arguments to the sub-command */ };
From include/uapi/linux/if.h
, the unsigned long arg passed with ioctl()
:
#if __UAPI_DEF_IF_IFREQ struct ifreq { #define IFHWADDRLEN 6 union { char ifrn_name[IFNAMSIZ]; /* if name, e.g. "en0" */ } ifr_ifrn; union { struct sockaddr ifru_addr; struct sockaddr ifru_dstaddr; struct sockaddr ifru_broadaddr; struct sockaddr ifru_netmask; struct sockaddr ifru_hwaddr; short ifru_flags; int ifru_ivalue; int ifru_mtu; struct ifmap ifru_map; char ifru_slave[IFNAMSIZ]; /* Just fits the size */ char ifru_newname[IFNAMSIZ]; void __user * ifru_data; struct if_settings ifru_settings; } ifr_ifru; }; #endif /* __UAPI_DEF_IF_IFREQ */ #define ifr_name ifr_ifrn.ifrn_name /* interface name */ #define ifr_hwaddr ifr_ifru.ifru_hwaddr /* MAC address */ #define ifr_addr ifr_ifru.ifru_addr /* address */ #define ifr_dstaddr ifr_ifru.ifru_dstaddr /* other end of p-p lnk */ #define ifr_broadaddr ifr_ifru.ifru_broadaddr /* broadcast address */ #define ifr_netmask ifr_ifru.ifru_netmask /* interface net mask */ #define ifr_flags ifr_ifru.ifru_flags /* flags */ #define ifr_metric ifr_ifru.ifru_ivalue /* metric */ #define ifr_mtu ifr_ifru.ifru_mtu /* mtu */ #define ifr_map ifr_ifru.ifru_map /* device map */ #define ifr_slave ifr_ifru.ifru_slave /* slave device */ #define ifr_data ifr_ifru.ifru_data /* for use by interface */ #define ifr_ifindex ifr_ifru.ifru_ivalue /* interface index */ #define ifr_bandwidth ifr_ifru.ifru_ivalue /* link bandwidth */ #define ifr_qlen ifr_ifru.ifru_ivalue /* Queue length */ #define ifr_newname ifr_ifru.ifru_newname /* New name */ #define ifr_settings ifr_ifru.ifru_settings /* Device/proto settings*/
From net/socket.c
:
static const struct file_operations socket_file_ops = { .owner = THIS_MODULE, .llseek = no_llseek, .read_iter = sock_read_iter, .write_iter = sock_write_iter, .poll = sock_poll, .unlocked_ioctl = sock_ioctl, <-- this one #ifdef CONFIG_COMPAT .compat_ioctl = compat_sock_ioctl, #endif .mmap = sock_mmap, .release = sock_close, .fasync = sock_fasync, .sendpage = sock_sendpage, .splice_write = generic_splice_sendpage, .splice_read = sock_splice_read, };
Also from net/socket.c
– anything related to SIOCDEVPRIVATE
is seriously deprecated (see here):
static long sock_ioctl(struct file *file, unsigned cmd, unsigned long arg) { struct socket *sock; struct sock *sk; void __user *argp = (void __user *)arg; int pid, err; struct net *net; sock = file->private_data; sk = sock->sk; net = sock_net(sk); if (unlikely(cmd >= SIOCDEVPRIVATE && cmd <= (SIOCDEVPRIVATE + 15))) { struct ifreq ifr; bool need_copyout; if (copy_from_user(&ifr, argp, sizeof(struct ifreq))) return -EFAULT; err = dev_ioctl(net, cmd, &ifr, &need_copyout); if (!err && need_copyout) if (copy_to_user(argp, &ifr, sizeof(struct ifreq))) return -EFAULT; } else
This reflects wireless extensions, which should not be relevant:
#ifdef CONFIG_WEXT_CORE if (cmd >= SIOCIWFIRST && cmd <= SIOCIWLAST) { err = wext_handle_ioctl(net, cmd, argp); } else #endif
Finally, this is where we should end up:
switch (cmd) { case FIOSETOWN: case SIOCSPGRP: err = -EFAULT; if (get_user(pid, (int __user *)argp)) break; err = f_setown(sock->file, pid, 1); break; case FIOGETOWN: case SIOCGPGRP: err = put_user(f_getown(sock->file), (int __user *)argp); break; case SIOCGIFBR: case SIOCSIFBR: case SIOCBRADDBR: case SIOCBRDELBR: err = -ENOPKG; if (!br_ioctl_hook) request_module("bridge"); mutex_lock(&br_ioctl_mutex); if (br_ioctl_hook) err = br_ioctl_hook(net, cmd, argp); mutex_unlock(&br_ioctl_mutex); break; case SIOCGIFVLAN: case SIOCSIFVLAN: err = -ENOPKG; if (!vlan_ioctl_hook) request_module("8021q"); mutex_lock(&vlan_ioctl_mutex); if (vlan_ioctl_hook) err = vlan_ioctl_hook(net, argp); mutex_unlock(&vlan_ioctl_mutex); break; case SIOCADDDLCI: case SIOCDELDLCI: err = -ENOPKG; if (!dlci_ioctl_hook) request_module("dlci"); mutex_lock(&dlci_ioctl_mutex); if (dlci_ioctl_hook) err = dlci_ioctl_hook(cmd, argp); mutex_unlock(&dlci_ioctl_mutex); break; case SIOCGSKNS: err = -EPERM; if (!ns_capable(net->user_ns, CAP_NET_ADMIN)) break; err = open_related_ns(&net->ns, get_net_ns); break; default: err = sock_do_ioctl(net, sock, cmd, arg); <-- there break; } return err; }
Still in net/socket.c
:
static long sock_do_ioctl(struct net *net, struct socket *sock, unsigned int cmd, unsigned long arg) { int err; void __user *argp = (void __user *)arg; err = sock->ops->ioctl(sock, cmd, arg); /* * If this ioctl is unknown try to hand it down * to the NIC driver. */ if (err != -ENOIOCTLCMD) return err; if (cmd == SIOCGIFCONF) { struct ifconf ifc; if (copy_from_user(&ifc, argp, sizeof(struct ifconf))) return -EFAULT; rtnl_lock(); err = dev_ifconf(net, &ifc, sizeof(struct ifreq)); rtnl_unlock(); if (!err && copy_to_user(argp, &ifc, sizeof(struct ifconf))) err = -EFAULT; } else { struct ifreq ifr; bool need_copyout; if (copy_from_user(&ifr, argp, sizeof(struct ifreq))) return -EFAULT; err = dev_ioctl(net, cmd, &ifr, &need_copyout); <-- here??? if (!err && need_copyout) if (copy_to_user(argp, &ifr, sizeof(struct ifreq))) return -EFAULT; } return err; }