1/* 2 * Copyright (C) 2011 The Android Open Source Project 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17/* NOTICE: This is a clean room re-implementation of libnl */ 18 19#include <malloc.h> 20#include <unistd.h> 21#include <sys/socket.h> 22#include <linux/netlink.h> 23#include "netlink-types.h" 24 25/* Allocate a new netlink message with the default maximum payload size. */ 26struct nl_msg *nlmsg_alloc(void) 27{ 28 /* Whole page will store nl_msg + nlmsghdr + genlmsghdr + payload */ 29 const int page_sz = getpagesize(); 30 struct nl_msg *nm; 31 struct nlmsghdr *nlh; 32 33 /* Netlink message */ 34 nm = (struct nl_msg *) malloc(page_sz); 35 if (!nm) 36 goto fail; 37 38 /* Netlink message header pointer */ 39 nlh = (struct nlmsghdr *) ((char *) nm + sizeof(struct nl_msg)); 40 41 /* Initialize */ 42 memset(nm, 0, page_sz); 43 nm->nm_size = page_sz; 44 45 nm->nm_src.nl_family = AF_NETLINK; 46 nm->nm_src.nl_pid = getpid(); 47 48 nm->nm_dst.nl_family = AF_NETLINK; 49 nm->nm_dst.nl_pid = 0; /* Kernel */ 50 51 /* Initialize and add to netlink message */ 52 nlh->nlmsg_len = NLMSG_HDRLEN; 53 nm->nm_nlh = nlh; 54 55 /* Add to reference count and return nl_msg */ 56 nlmsg_get(nm); 57 return nm; 58fail: 59 return NULL; 60} 61 62/* Return pointer to message payload. */ 63void *nlmsg_data(const struct nlmsghdr *nlh) 64{ 65 return (char *) nlh + NLMSG_HDRLEN; 66} 67 68/* Add reference count to nl_msg */ 69void nlmsg_get(struct nl_msg *nm) 70{ 71 nm->nm_refcnt++; 72} 73 74/* Release a reference from an netlink message. */ 75void nlmsg_free(struct nl_msg *nm) 76{ 77 if (nm) { 78 nm->nm_refcnt--; 79 if (nm->nm_refcnt <= 0) 80 free(nm); 81 } 82 83} 84 85/* Return actual netlink message. */ 86struct nlmsghdr *nlmsg_hdr(struct nl_msg *n) 87{ 88 return n->nm_nlh; 89} 90 91/* Return head of attributes data / payload section */ 92struct nlattr *nlmsg_attrdata(const struct nlmsghdr *nlh, int hdrlen) 93{ 94 unsigned char *data = nlmsg_data(nlh); 95 return (struct nlattr *)(data + NLMSG_ALIGN(hdrlen)); 96} 97 98/* Returns pointer to end of netlink message */ 99void *nlmsg_tail(const struct nlmsghdr *nlh) 100{ 101 return (void *)((char *)nlh + NLMSG_ALIGN(nlh->nlmsg_len)); 102} 103 104/* Next netlink message in message stream */ 105struct nlmsghdr *nlmsg_next(struct nlmsghdr *nlh, int *remaining) 106{ 107 struct nlmsghdr *next_nlh = NULL; 108 int len = nlmsg_len(nlh); 109 110 len = NLMSG_ALIGN(len); 111 if (*remaining > 0 && 112 len <= *remaining && 113 len >= (int) sizeof(struct nlmsghdr)) { 114 next_nlh = (struct nlmsghdr *)((char *)nlh + len); 115 *remaining -= len; 116 } 117 118 return next_nlh; 119} 120 121int nlmsg_datalen(const struct nlmsghdr *nlh) 122{ 123 return nlh->nlmsg_len - NLMSG_HDRLEN; 124} 125 126/* Length of attributes data */ 127int nlmsg_attrlen(const struct nlmsghdr *nlh, int hdrlen) 128{ 129 return nlmsg_datalen(nlh) - NLMSG_ALIGN(hdrlen); 130} 131 132/* Length of netlink message */ 133int nlmsg_len(const struct nlmsghdr *nlh) 134{ 135 return nlh->nlmsg_len; 136} 137 138/* Check if the netlink message fits into the remaining bytes */ 139int nlmsg_ok(const struct nlmsghdr *nlh, int rem) 140{ 141 return rem >= (int)sizeof(struct nlmsghdr) && 142 rem >= nlmsg_len(nlh) && 143 nlmsg_len(nlh) >= (int) sizeof(struct nlmsghdr) && 144 nlmsg_len(nlh) <= (rem); 145} 146 147int nlmsg_padlen(int payload) 148{ 149 return NLMSG_ALIGN(payload) - payload; 150} 151