static int verify_source (struct nl_msg *msg, gpointer user_data) { struct ucred *creds = nlmsg_get_creds (msg); if (!creds || creds->pid || creds->uid || creds->gid) { if (creds) g_warning ("netlink: received non-kernel message (pid %d uid %d gid %d)", creds->pid, creds->uid, creds->gid); else g_warning ("netlink: received message without credentials"); return NL_STOP; } return NL_OK; }
static int event_msg_recv (struct nl_msg *msg, void *arg) { struct nl_sock *nlh = arg; struct nlmsghdr *hdr = nlmsg_hdr (msg); struct ucred *creds = nlmsg_get_creds (msg); const struct sockaddr_nl *snl; guint32 local_port; gboolean accept_msg = FALSE; /* Only messages sent from the kernel */ if (!creds || creds->uid != 0) { nm_log_dbg (LOGD_HW, "ignoring netlink message from UID %d", creds ? creds->uid : -1); return NL_SKIP; } snl = nlmsg_get_src (msg); g_assert (snl); /* Accept any messages from the kernel */ if (hdr->nlmsg_pid == 0 || snl->nl_pid == 0) accept_msg = TRUE; /* And any multicast message directed to our netlink PID, since multicast * currently requires CAP_ADMIN to use. */ local_port = nl_socket_get_local_port (nlh); if ((hdr->nlmsg_pid == local_port) && snl->nl_groups) accept_msg = TRUE; if (accept_msg == FALSE) { nm_log_dbg (LOGD_HW, "ignoring netlink message from PID %d (local PID %d, multicast %d)", hdr->nlmsg_pid, local_port, (hdr->nlmsg_flags & NLM_F_MULTI)); return NL_SKIP; } return NL_OK; }
/** * Send netlink message. * @arg sk Netlink socket. * @arg msg Netlink message to be sent. * @arg iov iovec to be sent. * @arg iovlen number of struct iovec to be sent. * @see nl_sendmsg() * @return Number of characters sent on success or a negative error code. */ int nl_send_iovec(struct nl_sock *sk, struct nl_msg *msg, struct iovec *iov, unsigned iovlen) { struct sockaddr_nl *dst; struct ucred *creds; struct msghdr hdr = { .msg_name = (void *) &sk->s_peer, .msg_namelen = sizeof(struct sockaddr_nl), .msg_iov = iov, .msg_iovlen = iovlen, }; /* Overwrite destination if specified in the message itself, defaults * to the peer address of the socket. */ dst = nlmsg_get_dst(msg); if (dst->nl_family == AF_NETLINK) hdr.msg_name = dst; /* Add credentials if present. */ creds = nlmsg_get_creds(msg); if (creds != NULL) { char buf[CMSG_SPACE(sizeof(struct ucred))]; struct cmsghdr *cmsg; hdr.msg_control = buf; hdr.msg_controllen = sizeof(buf); cmsg = CMSG_FIRSTHDR(&hdr); cmsg->cmsg_level = SOL_SOCKET; cmsg->cmsg_type = SCM_CREDENTIALS; cmsg->cmsg_len = CMSG_LEN(sizeof(struct ucred)); memcpy(CMSG_DATA(cmsg), creds, sizeof(struct ucred)); } return nl_sendmsg(sk, msg, &hdr); } /** * Send netlink message. * @arg sk Netlink socket. * @arg msg Netlink message to be sent. * @see nl_sendmsg() * @return Number of characters sent on success or a negative error code. */ int nl_send(struct nl_sock *sk, struct nl_msg *msg) { struct iovec iov = { .iov_base = (void *) nlmsg_hdr(msg), .iov_len = nlmsg_hdr(msg)->nlmsg_len, }; return nl_send_iovec(sk, msg, &iov, 1); } void nl_complete_msg(struct nl_sock *sk, struct nl_msg *msg) { struct nlmsghdr *nlh; nlh = nlmsg_hdr(msg); if (nlh->nlmsg_pid == 0) nlh->nlmsg_pid = sk->s_local.nl_pid; if (nlh->nlmsg_seq == 0) nlh->nlmsg_seq = sk->s_seq_next++; if (msg->nm_protocol == -1) msg->nm_protocol = sk->s_proto; nlh->nlmsg_flags |= NLM_F_REQUEST; if (!(sk->s_flags & NL_NO_AUTO_ACK)) nlh->nlmsg_flags |= NLM_F_ACK; } void nl_auto_complete(struct nl_sock *sk, struct nl_msg *msg) { nl_complete_msg(sk, msg); } /** * Automatically complete and send a netlink message * @arg sk Netlink socket. * @arg msg Netlink message to be sent. * * This function takes a netlink message and passes it on to * nl_auto_complete() for completion. * * Checks the netlink message \c nlh for completness and extends it * as required before sending it out. Checked fields include pid, * sequence nr, and flags. * * @see nl_send() * @return Number of characters sent or a negative error code. */ int nl_send_auto(struct nl_sock *sk, struct nl_msg *msg) { struct nl_cb *cb = sk->s_cb; nl_complete_msg(sk, msg); if (cb->cb_send_ow) return cb->cb_send_ow(sk, msg); else return nl_send(sk, msg); } int nl_send_auto_complete(struct nl_sock *sk, struct nl_msg *msg) { return nl_send_auto(sk, msg); } /** * Send netlink message and wait for response (sync request-response) * @arg sk Netlink socket * @arg msg Netlink message to be sent * * This function takes a netlink message and sends it using nl_send_auto(). * It will then wait for the response (ACK or error message) to be * received. Threfore this function will block until the operation has * been completed. * * @note Disabling auto-ack (nl_socket_disable_auto_ack()) will cause * this function to return immediately after sending. In this case, * it is the responsibility of the caller to handle any eventual * error messages returned. * * @see nl_send_auto(). * * @return 0 on success or a negative error code. */ int nl_send_sync(struct nl_sock *sk, struct nl_msg *msg) { int err; err = nl_send_auto(sk, msg); nlmsg_free(msg); if (err < 0) return err; return wait_for_ack(sk); }
/** * Send netlink message with control over sendmsg() message header. * @arg handle Netlink handle. * @arg msg Netlink message to be sent. * @arg hdr Sendmsg() message header. * @return Number of characters sent on sucess or a negative error code. */ int nl_sendmsg(struct nl_handle *handle, struct nl_msg *msg, struct msghdr *hdr) { struct nl_cb *cb; int ret; struct iovec iov = { .iov_base = (void *) nlmsg_hdr(msg), .iov_len = nlmsg_hdr(msg)->nlmsg_len, }; hdr->msg_iov = &iov; hdr->msg_iovlen = 1; nlmsg_set_src(msg, &handle->h_local); cb = nl_handle_get_cb(handle); if (cb->cb_set[NL_CB_MSG_OUT]) if (nl_cb_call(cb, NL_CB_MSG_OUT, msg) != NL_PROCEED) return 0; ret = sendmsg(handle->h_fd, hdr, 0); if (ret < 0) return nl_errno(errno); return ret; } /** * Send netlink message. * @arg handle Netlink handle * @arg msg Netlink message to be sent. * @see nl_sendmsg() * @return Number of characters sent on success or a negative error code. */ int nl_send(struct nl_handle *handle, struct nl_msg *msg) { struct sockaddr_nl *dst; struct ucred *creds; struct msghdr hdr = { .msg_name = (void *) &handle->h_peer, .msg_namelen = sizeof(struct sockaddr_nl), }; /* Overwrite destination if specified in the message itself, defaults * to the peer address of the handle. */ dst = nlmsg_get_dst(msg); if (dst->nl_family == AF_NETLINK) hdr.msg_name = dst; /* Add credentials if present. */ creds = nlmsg_get_creds(msg); if (creds != NULL) { char buf[CMSG_SPACE(sizeof(struct ucred))]; struct cmsghdr *cmsg; hdr.msg_control = buf; hdr.msg_controllen = sizeof(buf); cmsg = CMSG_FIRSTHDR(&hdr); cmsg->cmsg_level = SOL_SOCKET; cmsg->cmsg_type = SCM_CREDENTIALS; cmsg->cmsg_len = CMSG_LEN(sizeof(struct ucred)); memcpy(CMSG_DATA(cmsg), creds, sizeof(struct ucred)); } return nl_sendmsg(handle, msg, &hdr); } /** * Send netlink message and check & extend header values as needed. * @arg handle Netlink handle. * @arg msg Netlink message to be sent. * * Checks the netlink message \c nlh for completness and extends it * as required before sending it out. Checked fields include pid, * sequence nr, and flags. * * @see nl_send() * @return Number of characters sent or a negative error code. */ int nl_send_auto_complete(struct nl_handle *handle, struct nl_msg *msg) { struct nlmsghdr *nlh; nlh = nlmsg_hdr(msg); if (nlh->nlmsg_pid == 0) nlh->nlmsg_pid = handle->h_local.nl_pid; if (nlh->nlmsg_seq == 0) nlh->nlmsg_seq = handle->h_seq_next++; nlh->nlmsg_flags |= (NLM_F_REQUEST | NLM_F_ACK); if (handle->h_cb->cb_send_ow) return handle->h_cb->cb_send_ow(handle, msg); else return nl_send(handle, msg); } /** * Send simple netlink message using nl_send_auto_complete() * @arg handle Netlink handle. * @arg type Netlink message type. * @arg flags Netlink message flags. * @arg buf Data buffer. * @arg size Size of data buffer. * * Builds a netlink message with the specified type and flags and * appends the specified data as payload to the message. * * @see nl_send_auto_complete() * @return Number of characters sent on success or a negative error code. */ int nl_send_simple(struct nl_handle *handle, int type, int flags, void *buf, size_t size) { int err; struct nl_msg *msg; struct nlmsghdr nlh = { .nlmsg_len = nlmsg_msg_size(0), .nlmsg_type = type, .nlmsg_flags = flags, }; msg = nlmsg_build(&nlh); if (!msg) return nl_errno(ENOMEM); if (buf && size) nlmsg_append(msg, buf, size, 1); err = nl_send_auto_complete(handle, msg); nlmsg_free(msg); return err; } /** @} */ /** * @name Receive * @{ */ /** * Receive netlink message from netlink socket. * @arg handle Netlink handle. * @arg nla Destination pointer for peer's netlink address. * @arg buf Destination pointer for message content. * @arg creds Destination pointer for credentials. * * Receives a netlink message, allocates a buffer in \c *buf and * stores the message content. The peer's netlink address is stored * in \c *nla. The caller is responsible for freeing the buffer allocated * in \c *buf if a positive value is returned. Interruped system calls * are handled by repeating the read. The input buffer size is determined * by peeking before the actual read is done. * * A non-blocking sockets causes the function to return immediately if * no data is available. * * @return Number of octets read, 0 on EOF or a negative error code. */ int nl_recv(struct nl_handle *handle, struct sockaddr_nl *nla, unsigned char **buf, struct ucred **creds) { int n; int flags = MSG_PEEK; struct iovec iov = { .iov_len = 4096, }; struct msghdr msg = { .msg_name = (void *) nla, .msg_namelen = sizeof(sizeof(struct sockaddr_nl)), .msg_iov = &iov, .msg_iovlen = 1, .msg_control = NULL, .msg_controllen = 0, .msg_flags = 0, }; struct cmsghdr *cmsg; iov.iov_base = *buf = calloc(1, iov.iov_len); if (handle->h_flags & NL_SOCK_PASSCRED) { msg.msg_controllen = CMSG_SPACE(sizeof(struct ucred)); msg.msg_control = calloc(1, msg.msg_controllen); } retry: if ((n = recvmsg(handle->h_fd, &msg, flags)) <= 0) { if (!n) goto abort; else if (n < 0) { if (errno == EINTR) goto retry; else if (errno == EAGAIN) goto abort; else { free(msg.msg_control); free(*buf); return nl_error(errno, "recvmsg failed"); } } } if (iov.iov_len < n) { /* Provided buffer is not long enough, enlarge it * and try again. */ iov.iov_len *= 2; iov.iov_base = *buf = realloc(*buf, iov.iov_len); goto retry; } else if (msg.msg_flags & MSG_CTRUNC) { msg.msg_controllen *= 2; msg.msg_control = realloc(msg.msg_control, msg.msg_controllen); goto retry; } else if (flags != 0) { /* Buffer is big enough, do the actual reading */ flags = 0; goto retry; } if (msg.msg_namelen != sizeof(struct sockaddr_nl)) { free(msg.msg_control); free(*buf); return nl_error(EADDRNOTAVAIL, "socket address size mismatch"); } for (cmsg = CMSG_FIRSTHDR(&msg); cmsg; cmsg = CMSG_NXTHDR(&msg, cmsg)) { if (cmsg->cmsg_level == SOL_SOCKET && cmsg->cmsg_type == SCM_CREDENTIALS) { *creds = calloc(1, sizeof(struct ucred)); memcpy(*creds, CMSG_DATA(cmsg), sizeof(struct ucred)); break; } } free(msg.msg_control); return n; abort: free(msg.msg_control); free(*buf); return 0; } /** * Receive a set of messages from a netlink socket. * @arg handle netlink handle * @arg cb set of callbacks to control the behaviour. * * Repeatedly calls nl_recv() and parses the messages as netlink * messages. Stops reading if one of the callbacks returns * NL_EXIT or nl_recv returns either 0 or a negative error code. * * A non-blocking sockets causes the function to return immediately if * no data is available. * * @return 0 on success or a negative error code from nl_recv(). */ int nl_recvmsgs(struct nl_handle *handle, struct nl_cb *cb) { int n, err = 0; unsigned char *buf = NULL; struct nlmsghdr *hdr; struct sockaddr_nl nla = {0}; struct nl_msg *msg = NULL; struct ucred *creds = NULL; continue_reading: if (cb->cb_recv_ow) n = cb->cb_recv_ow(handle, &nla, &buf, &creds); else n = nl_recv(handle, &nla, &buf, &creds); if (n <= 0) return n; NL_DBG(3, "recvmsgs(%p): Read %d bytes\n", handle, n); hdr = (struct nlmsghdr *) buf; while (nlmsg_ok(hdr, n)) { NL_DBG(3, "recgmsgs(%p): Processing valid message...\n", handle); nlmsg_free(msg); msg = nlmsg_convert(hdr); if (!msg) { err = nl_errno(ENOMEM); goto out; } nlmsg_set_proto(msg, handle->h_proto); nlmsg_set_src(msg, &nla); if (creds) nlmsg_set_creds(msg, creds); /* Raw callback is the first, it gives the most control * to the user and he can do his very own parsing. */ if (cb->cb_set[NL_CB_MSG_IN]) { err = nl_cb_call(cb, NL_CB_MSG_IN, msg); if (err == NL_SKIP) goto skip; else if (err == NL_EXIT || err < 0) goto out; } /* Sequence number checking. The check may be done by * the user, otherwise a very simple check is applied * enforcing strict ordering */ if (cb->cb_set[NL_CB_SEQ_CHECK]) { err = nl_cb_call(cb, NL_CB_SEQ_CHECK, msg); if (err == NL_SKIP) goto skip; else if (err == NL_EXIT || err < 0) goto out; } else if (hdr->nlmsg_seq != handle->h_seq_expect) { if (cb->cb_set[NL_CB_INVALID]) { err = nl_cb_call(cb, NL_CB_INVALID, msg); if (err == NL_SKIP) goto skip; else if (err == NL_EXIT || err < 0) goto out; } else goto out; } if (hdr->nlmsg_type == NLMSG_DONE || hdr->nlmsg_type == NLMSG_ERROR || hdr->nlmsg_type == NLMSG_NOOP || hdr->nlmsg_type == NLMSG_OVERRUN) { /* We can't check for !NLM_F_MULTI since some netlink * users in the kernel are broken. */ handle->h_seq_expect++; NL_DBG(3, "recvmsgs(%p): Increased expected " \ "sequence number to %d\n", handle, handle->h_seq_expect); } /* Other side wishes to see an ack for this message */ if (hdr->nlmsg_flags & NLM_F_ACK) { if (cb->cb_set[NL_CB_SEND_ACK]) { err = nl_cb_call(cb, NL_CB_SEND_ACK, msg); if (err == NL_SKIP) goto skip; else if (err == NL_EXIT || err < 0) goto out; } else { /* FIXME: implement */ } } /* messages terminates a multpart message, this is * usually the end of a message and therefore we slip * out of the loop by default. the user may overrule * this action by skipping this packet. */ if (hdr->nlmsg_type == NLMSG_DONE) { if (cb->cb_set[NL_CB_FINISH]) { err = nl_cb_call(cb, NL_CB_FINISH, msg); if (err == NL_SKIP) goto skip; else if (err == NL_EXIT || err < 0) goto out; } err = 0; goto out; } /* Message to be ignored, the default action is to * skip this message if no callback is specified. The * user may overrule this action by returning * NL_PROCEED. */ else if (hdr->nlmsg_type == NLMSG_NOOP) { if (cb->cb_set[NL_CB_SKIPPED]) { err = nl_cb_call(cb, NL_CB_SKIPPED, msg); if (err == NL_SKIP) goto skip; else if (err == NL_EXIT || err < 0) goto out; } else goto skip; } /* Data got lost, report back to user. The default action is to * quit parsing. The user may overrule this action by retuning * NL_SKIP or NL_PROCEED (dangerous) */ else if (hdr->nlmsg_type == NLMSG_OVERRUN) { if (cb->cb_set[NL_CB_OVERRUN]) { err = nl_cb_call(cb, NL_CB_OVERRUN, msg); if (err == NL_SKIP) goto skip; else if (err == NL_EXIT || err < 0) goto out; } else goto out; } /* Message carries a nlmsgerr */ else if (hdr->nlmsg_type == NLMSG_ERROR) { struct nlmsgerr *e = nlmsg_data(hdr); if (hdr->nlmsg_len < nlmsg_msg_size(sizeof(*e))) { /* Truncated error message, the default action * is to stop parsing. The user may overrule * this action by returning NL_SKIP or * NL_PROCEED (dangerous) */ if (cb->cb_set[NL_CB_INVALID]) { err = nl_cb_call(cb, NL_CB_INVALID, msg); if (err == NL_SKIP) goto skip; else if (err == NL_EXIT || err < 0) goto out; } else goto out; } else if (e->error) { /* Error message reported back from kernel. */ if (cb->cb_err) { err = cb->cb_err(&nla, e, cb->cb_err_arg); if (err == NL_SKIP) goto skip; else if (err == NL_EXIT || err < 0) { nl_error(-e->error, "Netlink Error"); err = e->error; goto out; } } else { nl_error(-e->error, "Netlink Error"); err = e->error; goto out; } } else if (cb->cb_set[NL_CB_ACK]) { /* ACK */ err = nl_cb_call(cb, NL_CB_ACK, msg); if (err == NL_SKIP) goto skip; else if (err == NL_EXIT || err < 0) goto out; } } else { /* Valid message (not checking for MULTIPART bit to * get along with broken kernels. NL_SKIP has no * effect on this. */ if (cb->cb_set[NL_CB_VALID]) { err = nl_cb_call(cb, NL_CB_VALID, msg); if (err == NL_SKIP) goto skip; else if (err == NL_EXIT || err < 0) goto out; } } skip: hdr = nlmsg_next(hdr, &n); } nlmsg_free(msg); free(buf); free(creds); buf = NULL; msg = NULL; creds = NULL; /* Multipart message not yet complete, continue reading */ goto continue_reading; out: nlmsg_free(msg); free(buf); free(creds); return err; } /** * Receive a set of message from a netlink socket using handlers in nl_handle. * @arg handle netlink handle * * Calls nl_recvmsgs() with the handlers configured in the netlink handle. */ int nl_recvmsgs_def(struct nl_handle *handle) { if (handle->h_cb->cb_recvmsgs_ow) return handle->h_cb->cb_recvmsgs_ow(handle, handle->h_cb); else return nl_recvmsgs(handle, handle->h_cb); } static int ack_wait_handler(struct nl_msg *msg, void *arg) { return NL_EXIT; } /** * Wait for ACK. * @arg handle netlink handle * @pre The netlink socket must be in blocking state. * * Waits until an ACK is received for the latest not yet acknowledged * netlink message. */ int nl_wait_for_ack(struct nl_handle *handle) { int err; struct nl_cb *cb = nl_cb_clone(nl_handle_get_cb(handle)); nl_cb_set(cb, NL_CB_ACK, NL_CB_CUSTOM, ack_wait_handler, NULL); err = nl_recvmsgs(handle, cb); nl_cb_destroy(cb); return err; } /** @} */ /** * @name Netlink Family Translations * @{ */ static struct trans_tbl nlfamilies[] = { __ADD(NETLINK_ROUTE,route) __ADD(NETLINK_W1,w1) __ADD(NETLINK_USERSOCK,usersock) __ADD(NETLINK_FIREWALL,firewall) __ADD(NETLINK_INET_DIAG,inetdiag) __ADD(NETLINK_NFLOG,nflog) __ADD(NETLINK_XFRM,xfrm) __ADD(NETLINK_SELINUX,selinux) __ADD(NETLINK_ISCSI,iscsi) __ADD(NETLINK_AUDIT,audit) __ADD(NETLINK_FIB_LOOKUP,fib_lookup) __ADD(NETLINK_CONNECTOR,connector) __ADD(NETLINK_NETFILTER,netfilter) __ADD(NETLINK_IP6_FW,ip6_fw) __ADD(NETLINK_DNRTMSG,dnrtmsg) __ADD(NETLINK_KOBJECT_UEVENT,kobject_uevent) __ADD(NETLINK_GENERIC,generic) }; /** * Convert netlink family to character string. * @arg family Netlink family. * @arg buf Destination buffer. * @arg size Size of destination buffer. * * Converts a netlink family to a character string and stores it in * the specified destination buffer. * * @return The destination buffer or the family encoded in hexidecimal * form if no match was found. */ char * nl_nlfamily2str(int family, char *buf, size_t size) { return __type2str(family, buf, size, nlfamilies, ARRAY_SIZE(nlfamilies)); } /** * Convert character string to netlink family. * @arg name Name of netlink family. * * Converts the provided character string specifying a netlink * family to the corresponding numeric value. * * @return Numeric netlink family or a negative value if no match was found. */ int nl_str2nlfamily(const char *name) { return __str2type(name, nlfamilies, ARRAY_SIZE(nlfamilies)); }
/** * Send netlink message. * @arg sk Netlink socket. * @arg msg Netlink message to be sent. * @arg iov iovec to be sent. * @arg iovlen number of struct iovec to be sent. * @see nl_sendmsg() * @return Number of characters sent on success or a negative error code. */ int nl_send_iovec(struct nl_sock *sk, struct nl_msg *msg, struct iovec *iov, unsigned iovlen) { struct sockaddr_nl *dst; struct ucred *creds; struct msghdr hdr = { .msg_name = (void *) &sk->s_peer, .msg_namelen = sizeof(struct sockaddr_nl), .msg_iov = iov, .msg_iovlen = iovlen, }; /* Overwrite destination if specified in the message itself, defaults * to the peer address of the socket. */ dst = nlmsg_get_dst(msg); if (dst->nl_family == AF_NETLINK) hdr.msg_name = dst; /* Add credentials if present. */ creds = nlmsg_get_creds(msg); if (creds != NULL) { char buf[CMSG_SPACE(sizeof(struct ucred))]; struct cmsghdr *cmsg; hdr.msg_control = buf; hdr.msg_controllen = sizeof(buf); cmsg = CMSG_FIRSTHDR(&hdr); cmsg->cmsg_level = SOL_SOCKET; cmsg->cmsg_type = SCM_CREDENTIALS; cmsg->cmsg_len = CMSG_LEN(sizeof(struct ucred)); memcpy(CMSG_DATA(cmsg), creds, sizeof(struct ucred)); } return nl_sendmsg(sk, msg, &hdr); } /** * Send netlink message. * @arg sk Netlink socket. * @arg msg Netlink message to be sent. * @see nl_sendmsg() * @return Number of characters sent on success or a negative error code. */ int nl_send(struct nl_sock *sk, struct nl_msg *msg) { struct iovec iov = { .iov_base = (void *) nlmsg_hdr(msg), .iov_len = nlmsg_hdr(msg)->nlmsg_len, }; return nl_send_iovec(sk, msg, &iov, 1); } void nl_auto_complete(struct nl_sock *sk, struct nl_msg *msg) { struct nlmsghdr *nlh; nlh = nlmsg_hdr(msg); if (nlh->nlmsg_pid == 0) nlh->nlmsg_pid = sk->s_local.nl_pid; if (nlh->nlmsg_seq == 0) nlh->nlmsg_seq = sk->s_seq_next++; if (msg->nm_protocol == -1) msg->nm_protocol = sk->s_proto; nlh->nlmsg_flags |= NLM_F_REQUEST; if (!(sk->s_flags & NL_NO_AUTO_ACK)) nlh->nlmsg_flags |= NLM_F_ACK; } /** * Send netlink message and check & extend header values as needed. * @arg sk Netlink socket. * @arg msg Netlink message to be sent. * * Checks the netlink message \c nlh for completness and extends it * as required before sending it out. Checked fields include pid, * sequence nr, and flags. * * @see nl_send() * @return Number of characters sent or a negative error code. */ int nl_send_auto_complete(struct nl_sock *sk, struct nl_msg *msg) { struct nl_cb *cb = sk->s_cb; nl_auto_complete(sk, msg); if (cb->cb_send_ow) return cb->cb_send_ow(sk, msg); else return nl_send(sk, msg); } /** * Send simple netlink message using nl_send_auto_complete() * @arg sk Netlink socket. * @arg type Netlink message type. * @arg flags Netlink message flags. * @arg buf Data buffer. * @arg size Size of data buffer. * * Builds a netlink message with the specified type and flags and * appends the specified data as payload to the message. * * @see nl_send_auto_complete() * @return Number of characters sent on success or a negative error code. */ int nl_send_simple(struct nl_sock *sk, int type, int flags, void *buf, size_t size) { int err; struct nl_msg *msg; msg = nlmsg_alloc_simple(type, flags); if (!msg) return -NLE_NOMEM; if (buf && size) { err = nlmsg_append(msg, buf, size, NLMSG_ALIGNTO); if (err < 0) goto errout; } err = nl_send_auto_complete(sk, msg); errout: nlmsg_free(msg); return err; } /** @} */ /** * @name Receive * @{ */ /** * Receive data from netlink socket * @arg sk Netlink socket. * @arg nla Destination pointer for peer's netlink address. * @arg buf Destination pointer for message content. * @arg creds Destination pointer for credentials. * * Receives a netlink message, allocates a buffer in \c *buf and * stores the message content. The peer's netlink address is stored * in \c *nla. The caller is responsible for freeing the buffer allocated * in \c *buf if a positive value is returned. Interruped system calls * are handled by repeating the read. The input buffer size is determined * by peeking before the actual read is done. * * A non-blocking sockets causes the function to return immediately with * a return value of 0 if no data is available. * * @return Number of octets read, 0 on EOF or a negative error code. */ int nl_recv(struct nl_sock *sk, struct sockaddr_nl *nla, unsigned char **buf, struct ucred **creds) { int n; int flags = 0; static int page_size = 0; struct iovec iov; struct msghdr msg = { .msg_name = (void *) nla, .msg_namelen = sizeof(struct sockaddr_nl), .msg_iov = &iov, .msg_iovlen = 1, .msg_control = NULL, .msg_controllen = 0, .msg_flags = 0, }; struct cmsghdr *cmsg; if (sk->s_flags & NL_MSG_PEEK) flags |= MSG_PEEK; if (page_size == 0) page_size = getpagesize(); iov.iov_len = page_size; iov.iov_base = *buf = malloc(iov.iov_len); if (sk->s_flags & NL_SOCK_PASSCRED) { msg.msg_controllen = CMSG_SPACE(sizeof(struct ucred)); msg.msg_control = calloc(1, msg.msg_controllen); } retry: n = recvmsg(sk->s_fd, &msg, flags); if (!n) goto abort; else if (n < 0) { if (errno == EINTR) { NL_DBG(3, "recvmsg() returned EINTR, retrying\n"); goto retry; } else if (errno == EAGAIN) { NL_DBG(3, "recvmsg() returned EAGAIN, aborting\n"); goto abort; } else { free(msg.msg_control); free(*buf); return -nl_syserr2nlerr(errno); } } if (iov.iov_len < n || msg.msg_flags & MSG_TRUNC) { /* Provided buffer is not long enough, enlarge it * and try again. */ iov.iov_len *= 2; iov.iov_base = *buf = realloc(*buf, iov.iov_len); goto retry; } else if (msg.msg_flags & MSG_CTRUNC) { msg.msg_controllen *= 2; msg.msg_control = realloc(msg.msg_control, msg.msg_controllen); goto retry; } else if (flags != 0) { /* Buffer is big enough, do the actual reading */ flags = 0; goto retry; } if (msg.msg_namelen != sizeof(struct sockaddr_nl)) { free(msg.msg_control); free(*buf); return -NLE_NOADDR; } for (cmsg = CMSG_FIRSTHDR(&msg); cmsg; cmsg = CMSG_NXTHDR(&msg, cmsg)) { if (cmsg->cmsg_level == SOL_SOCKET && cmsg->cmsg_type == SCM_CREDENTIALS) { *creds = calloc(1, sizeof(struct ucred)); memcpy(*creds, CMSG_DATA(cmsg), sizeof(struct ucred)); break; } } free(msg.msg_control); return n; abort: free(msg.msg_control); free(*buf); return 0; } #define NL_CB_CALL(cb, type, msg) \ do { \ err = nl_cb_call(cb, type, msg); \ switch (err) { \ case NL_OK: \ err = 0; \ break; \ case NL_SKIP: \ goto skip; \ case NL_STOP: \ goto stop; \ default: \ goto out; \ } \ } while (0) static int recvmsgs(struct nl_sock *sk, struct nl_cb *cb) { int n, err = 0, multipart = 0; unsigned char *buf = NULL; struct nlmsghdr *hdr; struct sockaddr_nl nla = {0}; struct nl_msg *msg = NULL; struct ucred *creds = NULL; continue_reading: NL_DBG(3, "Attempting to read from %p\n", sk); if (cb->cb_recv_ow) n = cb->cb_recv_ow(sk, &nla, &buf, &creds); else n = nl_recv(sk, &nla, &buf, &creds); if (n <= 0) return n; NL_DBG(3, "recvmsgs(%p): Read %d bytes\n", sk, n); hdr = (struct nlmsghdr *) buf; while (nlmsg_ok(hdr, n)) { NL_DBG(3, "recgmsgs(%p): Processing valid message...\n", sk); nlmsg_free(msg); msg = nlmsg_convert(hdr); if (!msg) { err = -NLE_NOMEM; goto out; } nlmsg_set_proto(msg, sk->s_proto); nlmsg_set_src(msg, &nla); if (creds) nlmsg_set_creds(msg, creds); /* Raw callback is the first, it gives the most control * to the user and he can do his very own parsing. */ if (cb->cb_set[NL_CB_MSG_IN]) NL_CB_CALL(cb, NL_CB_MSG_IN, msg); /* Sequence number checking. The check may be done by * the user, otherwise a very simple check is applied * enforcing strict ordering */ if (cb->cb_set[NL_CB_SEQ_CHECK]) NL_CB_CALL(cb, NL_CB_SEQ_CHECK, msg); else if (hdr->nlmsg_seq != sk->s_seq_expect) { if (cb->cb_set[NL_CB_INVALID]) NL_CB_CALL(cb, NL_CB_INVALID, msg); else { err = -NLE_SEQ_MISMATCH; goto out; } } if (hdr->nlmsg_type == NLMSG_DONE || hdr->nlmsg_type == NLMSG_ERROR || hdr->nlmsg_type == NLMSG_NOOP || hdr->nlmsg_type == NLMSG_OVERRUN) { /* We can't check for !NLM_F_MULTI since some netlink * users in the kernel are broken. */ sk->s_seq_expect++; NL_DBG(3, "recvmsgs(%p): Increased expected " \ "sequence number to %d\n", sk, sk->s_seq_expect); } if (hdr->nlmsg_flags & NLM_F_MULTI) multipart = 1; /* Other side wishes to see an ack for this message */ if (hdr->nlmsg_flags & NLM_F_ACK) { if (cb->cb_set[NL_CB_SEND_ACK]) NL_CB_CALL(cb, NL_CB_SEND_ACK, msg); else { /* FIXME: implement */ } } /* messages terminates a multpart message, this is * usually the end of a message and therefore we slip * out of the loop by default. the user may overrule * this action by skipping this packet. */ if (hdr->nlmsg_type == NLMSG_DONE) { multipart = 0; if (cb->cb_set[NL_CB_FINISH]) NL_CB_CALL(cb, NL_CB_FINISH, msg); } /* Message to be ignored, the default action is to * skip this message if no callback is specified. The * user may overrule this action by returning * NL_PROCEED. */ else if (hdr->nlmsg_type == NLMSG_NOOP) { if (cb->cb_set[NL_CB_SKIPPED]) NL_CB_CALL(cb, NL_CB_SKIPPED, msg); else goto skip; } /* Data got lost, report back to user. The default action is to * quit parsing. The user may overrule this action by retuning * NL_SKIP or NL_PROCEED (dangerous) */ else if (hdr->nlmsg_type == NLMSG_OVERRUN) { if (cb->cb_set[NL_CB_OVERRUN]) NL_CB_CALL(cb, NL_CB_OVERRUN, msg); else { err = -NLE_MSG_OVERFLOW; goto out; } } /* Message carries a nlmsgerr */ else if (hdr->nlmsg_type == NLMSG_ERROR) { struct nlmsgerr *e = nlmsg_data(hdr); if (hdr->nlmsg_len < nlmsg_msg_size(sizeof(*e))) { /* Truncated error message, the default action * is to stop parsing. The user may overrule * this action by returning NL_SKIP or * NL_PROCEED (dangerous) */ if (cb->cb_set[NL_CB_INVALID]) NL_CB_CALL(cb, NL_CB_INVALID, msg); else { err = -NLE_MSG_TRUNC; goto out; } } else if (e->error) { /* Error message reported back from kernel. */ if (cb->cb_err) { err = cb->cb_err(&nla, e, cb->cb_err_arg); if (err < 0) goto out; else if (err == NL_SKIP) goto skip; else if (err == NL_STOP) { err = -nl_syserr2nlerr(e->error); goto out; } } else { err = -nl_syserr2nlerr(e->error); goto out; } } else if (cb->cb_set[NL_CB_ACK]) NL_CB_CALL(cb, NL_CB_ACK, msg); } else { /* Valid message (not checking for MULTIPART bit to * get along with broken kernels. NL_SKIP has no * effect on this. */ if (cb->cb_set[NL_CB_VALID]) NL_CB_CALL(cb, NL_CB_VALID, msg); } skip: err = 0; hdr = nlmsg_next(hdr, &n); } nlmsg_free(msg); free(buf); free(creds); buf = NULL; msg = NULL; creds = NULL; if (multipart) { /* Multipart message not yet complete, continue reading */ goto continue_reading; } stop: err = 0; out: nlmsg_free(msg); free(buf); free(creds); return err; }
/** * Transmit Netlink message (taking IO vector) * @arg sk Netlink socket (required) * @arg msg Netlink message to be sent (required) * @arg iov IO vector to be sent (required) * @arg iovlen Number of struct iovec to be sent (required) * * This function is identical to nl_send() except that instead of taking a * `struct nl_msg` object it takes an IO vector. Please see the description * of `nl_send()`. * * @callback This function triggers the `NL_CB_MSG_OUT` callback. * * @see nl_send() * * @return Number of bytes sent on success or a negative error code. * * @lowlevel */ int nl_send_iovec(struct nl_sock *sk, struct nl_msg *msg, struct iovec *iov, unsigned iovlen) { struct sockaddr_nl *dst; struct ucred *creds; struct msghdr hdr = { .msg_name = (void *) &sk->s_peer, .msg_namelen = sizeof(struct sockaddr_nl), .msg_iov = iov, .msg_iovlen = iovlen, }; /* Overwrite destination if specified in the message itself, defaults * to the peer address of the socket. */ dst = nlmsg_get_dst(msg); if (dst->nl_family == AF_NETLINK) hdr.msg_name = dst; /* Add credentials if present. */ creds = nlmsg_get_creds(msg); if (creds != NULL) { char buf[CMSG_SPACE(sizeof(struct ucred))]; struct cmsghdr *cmsg; hdr.msg_control = buf; hdr.msg_controllen = sizeof(buf); cmsg = CMSG_FIRSTHDR(&hdr); cmsg->cmsg_level = SOL_SOCKET; cmsg->cmsg_type = SCM_CREDENTIALS; cmsg->cmsg_len = CMSG_LEN(sizeof(struct ucred)); memcpy(CMSG_DATA(cmsg), creds, sizeof(struct ucred)); } return nl_sendmsg(sk, msg, &hdr); } /** * Transmit Netlink message * @arg sk Netlink socket (required) * @arg msg Netlink message (required) * * Transmits the Netlink message `msg` over the Netlink socket using the * `sendmsg()` system call. This function is based on `nl_send_iovec()` but * takes care of initializing a `struct iovec` based on the `msg` object. * * The message is addressed to the peer as specified in the socket by either * the nl_socket_set_peer_port() or nl_socket_set_peer_groups() function. * The peer address can be overwritten by specifying an address in the `msg` * object using nlmsg_set_dst(). * * If present in the `msg`, credentials set by the nlmsg_set_creds() function * are added to the control buffer of the message. * * @par Overwriting Capability: * Calls to this function can be overwritten by providing an alternative using * the nl_cb_overwrite_send() function. * * @callback This function triggers the `NL_CB_MSG_OUT` callback. * * @attention * Unlike `nl_send_auto()`, this function does *not* finalize the message in * terms of automatically adding needed flags or filling out port numbers. * * @see nl_send_auto() * @see nl_send_iovec() * @see nl_socket_set_peer_port() * @see nl_socket_set_peer_groups() * @see nlmsg_set_dst() * @see nlmsg_set_creds() * @see nl_cb_overwrite_send() * * @return Number of bytes sent on success or a negative error code. */ int nl_send(struct nl_sock *sk, struct nl_msg *msg) { struct nl_cb *cb = sk->s_cb; if (cb->cb_send_ow) return cb->cb_send_ow(sk, msg); else { struct iovec iov = { .iov_base = (void *) nlmsg_hdr(msg), .iov_len = nlmsg_hdr(msg)->nlmsg_len, }; return nl_send_iovec(sk, msg, &iov, 1); } } /** * Finalize Netlink message * @arg sk Netlink socket (required) * @arg msg Netlink message (required) * * This function finalizes a Netlink message by completing the message with * desirable flags and values depending on the socket configuration. * * - If not yet filled out, the source address of the message (`nlmsg_pid`) * will be set to the local port number of the socket. * - If not yet specified, the next available sequence number is assigned * to the message (`nlmsg_seq`). * - If not yet specified, the protocol field of the message will be set to * the protocol field of the socket. * - The `NLM_F_REQUEST` Netlink message flag will be set. * - The `NLM_F_ACK` flag will be set if Auto-ACK mode is enabled on the * socket. */ void nl_complete_msg(struct nl_sock *sk, struct nl_msg *msg) { struct nlmsghdr *nlh; nlh = nlmsg_hdr(msg); if (nlh->nlmsg_pid == NL_AUTO_PORT) nlh->nlmsg_pid = nl_socket_get_local_port(sk); if (nlh->nlmsg_seq == NL_AUTO_SEQ) nlh->nlmsg_seq = sk->s_seq_next++; if (msg->nm_protocol == -1) msg->nm_protocol = sk->s_proto; nlh->nlmsg_flags |= NLM_F_REQUEST; if (!(sk->s_flags & NL_NO_AUTO_ACK)) nlh->nlmsg_flags |= NLM_F_ACK; } /** * Finalize and transmit Netlink message * @arg sk Netlink socket (required) * @arg msg Netlink message (required) * * Finalizes the message by passing it to `nl_complete_msg()` and transmits it * by passing it to `nl_send()`. * * @callback This function triggers the `NL_CB_MSG_OUT` callback. * * @see nl_complete_msg() * @see nl_send() * * @return Number of bytes sent or a negative error code. */ int nl_send_auto(struct nl_sock *sk, struct nl_msg *msg) { nl_complete_msg(sk, msg); return nl_send(sk, msg); } /** * Finalize and transmit Netlink message and wait for ACK or error message * @arg sk Netlink socket (required) * @arg msg Netlink message (required) * * Passes the `msg` to `nl_send_auto()` to finalize and transmit it. Frees the * message and waits (sleeps) for the ACK or error message to be received. * * @attention * Disabling Auto-ACK (nl_socket_disable_auto_ack()) will cause this function * to return immediately after transmitting the message. However, the peer may * still be returning an error message in response to the request. It is the * responsibility of the caller to handle such messages. * * @callback This function triggers the `NL_CB_MSG_OUT` callback. * * @attention * This function frees the `msg` object after transmitting it by calling * `nlmsg_free()`. * * @see nl_send_auto(). * @see nl_wait_for_ack() * * @return 0 on success or a negative error code. */ int nl_send_sync(struct nl_sock *sk, struct nl_msg *msg) { int err; err = nl_send_auto(sk, msg); nlmsg_free(msg); if (err < 0) return err; return wait_for_ack(sk); }