From 9c8309d4e129a994141871ffc5825b4f616c0b21 Mon Sep 17 00:00:00 2001 From: rofl0r Date: Thu, 10 Jul 2014 18:23:28 +0200 Subject: move files into toplevel dir --- nl.c | 720 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 720 insertions(+) create mode 100644 nl.c (limited to 'nl.c') diff --git a/nl.c b/nl.c new file mode 100644 index 0000000..99e9aeb --- /dev/null +++ b/nl.c @@ -0,0 +1,720 @@ +/* + * lib/nl.c Core Netlink Interface + * + * This library is free software; you can redistribute it and/or + * modify it under the terms of the GNU Lesser General Public + * License as published by the Free Software Foundation version 2.1 + * of the License. + * + * Copyright (c) 2003-2008 Thomas Graf + */ + +/** + * @defgroup core Core + * + * @details + * @par 1) Connecting the socket + * @code + * // Bind and connect the socket to a protocol, NETLINK_ROUTE in this example. + * nl_connect(sk, NETLINK_ROUTE); + * @endcode + * + * @par 2) Sending data + * @code + * // The most rudimentary method is to use nl_sendto() simply pushing + * // a piece of data to the other netlink peer. This method is not + * // recommended. + * const char buf[] = { 0x01, 0x02, 0x03, 0x04 }; + * nl_sendto(sk, buf, sizeof(buf)); + * + * // A more comfortable interface is nl_send() taking a pointer to + * // a netlink message. + * struct nl_msg *msg = my_msg_builder(); + * nl_send(sk, nlmsg_hdr(msg)); + * + * // nl_sendmsg() provides additional control over the sendmsg() message + * // header in order to allow more specific addressing of multiple peers etc. + * struct msghdr hdr = { ... }; + * nl_sendmsg(sk, nlmsg_hdr(msg), &hdr); + * + * // You're probably too lazy to fill out the netlink pid, sequence number + * // and message flags all the time. nl_send_auto_complete() automatically + * // extends your message header as needed with an appropriate sequence + * // number, the netlink pid stored in the netlink socket and the message + * // flags NLM_F_REQUEST and NLM_F_ACK (if not disabled in the socket) + * nl_send_auto_complete(sk, nlmsg_hdr(msg)); + * + * // Simple protocols don't require the complex message construction interface + * // and may favour nl_send_simple() to easly send a bunch of payload + * // encapsulated in a netlink message header. + * nl_send_simple(sk, MY_MSG_TYPE, 0, buf, sizeof(buf)); + * @endcode + * + * @par 3) Receiving data + * @code + * // nl_recv() receives a single message allocating a buffer for the message + * // content and gives back the pointer to you. + * struct sockaddr_nl peer; + * unsigned char *msg; + * nl_recv(sk, &peer, &msg); + * + * // nl_recvmsgs() receives a bunch of messages until the callback system + * // orders it to state, usually after receving a compolete multi part + * // message series. + * nl_recvmsgs(sk, my_callback_configuration); + * + * // nl_recvmsgs_default() acts just like nl_recvmsg() but uses the callback + * // configuration stored in the socket. + * nl_recvmsgs_default(sk); + * + * // In case you want to wait for the ACK to be recieved that you requested + * // with your latest message, you can call nl_wait_for_ack() + * nl_wait_for_ack(sk); + * @endcode + * + * @par 4) Closing + * @code + * // Close the socket first to release kernel memory + * nl_close(sk); + * @endcode + * + * @{ + */ + +#include +#include +#include +#include +#include +#include + +/** + * @name Connection Management + * @{ + */ + +/** + * Create and connect netlink socket. + * @arg sk Netlink socket. + * @arg protocol Netlink protocol to use. + * + * Creates a netlink socket using the specified protocol, binds the socket + * and issues a connection attempt. + * + * @return 0 on success or a negative error code. + */ +int nl_connect(struct nl_sock *sk, int protocol) +{ + int err; + socklen_t addrlen; + + sk->s_fd = socket(AF_NETLINK, SOCK_RAW, protocol); + if (sk->s_fd < 0) { + err = -nl_syserr2nlerr(errno); + goto errout; + } + + if (!(sk->s_flags & NL_SOCK_BUFSIZE_SET)) { + err = nl_socket_set_buffer_size(sk, 0, 0); + if (err < 0) + goto errout; + } + + err = bind(sk->s_fd, (struct sockaddr*) &sk->s_local, + sizeof(sk->s_local)); + if (err < 0) { + err = -nl_syserr2nlerr(errno); + goto errout; + } + + addrlen = sizeof(sk->s_local); + err = getsockname(sk->s_fd, (struct sockaddr *) &sk->s_local, + &addrlen); + if (err < 0) { + err = -nl_syserr2nlerr(errno); + goto errout; + } + + if (addrlen != sizeof(sk->s_local)) { + err = -NLE_NOADDR; + goto errout; + } + + if (sk->s_local.nl_family != AF_NETLINK) { + err = -NLE_AF_NOSUPPORT; + goto errout; + } + + sk->s_proto = protocol; + + return 0; +errout: + close(sk->s_fd); + sk->s_fd = -1; + + return err; +} + +/** + * Close/Disconnect netlink socket. + * @arg sk Netlink socket. + */ +void nl_close(struct nl_sock *sk) +{ + if (sk->s_fd >= 0) { + close(sk->s_fd); + sk->s_fd = -1; + } + + sk->s_proto = 0; +} + +/** @} */ + +/** + * @name Send + * @{ + */ + +/** + * Send raw data over netlink socket. + * @arg sk Netlink socket. + * @arg buf Data buffer. + * @arg size Size of data buffer. + * @return Number of characters written on success or a negative error code. + */ +int nl_sendto(struct nl_sock *sk, void *buf, size_t size) +{ + int ret; + + ret = sendto(sk->s_fd, buf, size, 0, (struct sockaddr *) + &sk->s_peer, sizeof(sk->s_peer)); + if (ret < 0) + return -nl_syserr2nlerr(errno); + + return ret; +} + +/** + * Send netlink message with control over sendmsg() message header. + * @arg sk Netlink socket. + * @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_sock *sk, 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, &sk->s_local); + + cb = sk->s_cb; + if (cb->cb_set[NL_CB_MSG_OUT]) + if (nl_cb_call(cb, NL_CB_MSG_OUT, msg) != NL_OK) + return 0; + + ret = sendmsg(sk->s_fd, hdr, 0); + if (ret < 0) + return -nl_syserr2nlerr(errno); + + return ret; +} + + +/** + * 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 sockaddr_nl *dst; + struct ucred *creds; + + struct msghdr hdr = { + .msg_name = (void *) &sk->s_peer, + .msg_namelen = sizeof(struct sockaddr_nl), + }; + + /* 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 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 nlmsghdr *nlh; + struct nl_cb *cb = sk->s_cb; + + 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; + + 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; +} + +/** + * Receive a set of messages from a netlink socket. + * @arg sk Netlink socket. + * @arg cb set of callbacks to control behaviour. + * + * Repeatedly calls nl_recv() or the respective replacement if provided + * by the application (see nl_cb_overwrite_recv()) and parses the + * received data as netlink messages. Stops reading if one of the + * callbacks returns NL_STOP 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_sock *sk, struct nl_cb *cb) +{ + if (cb->cb_recvmsgs_ow) + return cb->cb_recvmsgs_ow(sk, cb); + else + return recvmsgs(sk, cb); +} + + +static int ack_wait_handler(struct nl_msg *msg, void *arg) +{ + return NL_STOP; +} + +/** + * Wait for ACK. + * @arg sk Netlink socket. + * @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_sock *sk) +{ + int err; + struct nl_cb *cb; + + cb = nl_cb_clone(sk->s_cb); + if (cb == NULL) + return -NLE_NOMEM; + + nl_cb_set(cb, NL_CB_ACK, NL_CB_CUSTOM, ack_wait_handler, NULL); + err = nl_recvmsgs(sk, cb); + nl_cb_put(cb); + + return err; +} + +/** @} */ + +/** @} */ -- cgit v1.2.1