1 /*
2  * Copyright (C) 2008 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 #include <stdlib.h>
17 #include <string.h>
18 
19 #define LOG_TAG "NetlinkEvent"
20 #include <cutils/log.h>
21 
22 #include <sysutils/NetlinkEvent.h>
23 
24 #include <sys/types.h>
25 #include <sys/socket.h>
26 #include <netinet/in.h>
27 #include <netinet/icmp6.h>
28 #include <arpa/inet.h>
29 #include <net/if.h>
30 
31 #include <linux/if.h>
32 #include <linux/if_addr.h>
33 #include <linux/if_link.h>
34 #include <linux/netfilter/nfnetlink.h>
35 #include <linux/netfilter/nfnetlink_log.h>
36 #include <linux/netfilter_ipv4/ipt_ULOG.h>
37 
38 /* From kernel's net/netfilter/xt_quota2.c */
39 const int LOCAL_QLOG_NL_EVENT = 112;
40 const int LOCAL_NFLOG_PACKET = NFNL_SUBSYS_ULOG << 8 | NFULNL_MSG_PACKET;
41 
42 #include <linux/netlink.h>
43 #include <linux/rtnetlink.h>
44 
45 #include <netlink/attr.h>
46 #include <netlink/genl/genl.h>
47 #include <netlink/handlers.h>
48 #include <netlink/msg.h>
49 
NetlinkEvent()50 NetlinkEvent::NetlinkEvent() {
51     mAction = Action::kUnknown;
52     memset(mParams, 0, sizeof(mParams));
53     mPath = NULL;
54     mSubsystem = NULL;
55 }
56 
~NetlinkEvent()57 NetlinkEvent::~NetlinkEvent() {
58     int i;
59     if (mPath)
60         free(mPath);
61     if (mSubsystem)
62         free(mSubsystem);
63     for (i = 0; i < NL_PARAMS_MAX; i++) {
64         if (!mParams[i])
65             break;
66         free(mParams[i]);
67     }
68 }
69 
dump()70 void NetlinkEvent::dump() {
71     int i;
72 
73     for (i = 0; i < NL_PARAMS_MAX; i++) {
74         if (!mParams[i])
75             break;
76         SLOGD("NL param '%s'\n", mParams[i]);
77     }
78 }
79 
80 /*
81  * Returns the message name for a message in the NETLINK_ROUTE family, or NULL
82  * if parsing that message is not supported.
83  */
rtMessageName(int type)84 static const char *rtMessageName(int type) {
85 #define NL_EVENT_RTM_NAME(rtm) case rtm: return #rtm;
86     switch (type) {
87         NL_EVENT_RTM_NAME(RTM_NEWLINK);
88         NL_EVENT_RTM_NAME(RTM_DELLINK);
89         NL_EVENT_RTM_NAME(RTM_NEWADDR);
90         NL_EVENT_RTM_NAME(RTM_DELADDR);
91         NL_EVENT_RTM_NAME(RTM_NEWROUTE);
92         NL_EVENT_RTM_NAME(RTM_DELROUTE);
93         NL_EVENT_RTM_NAME(RTM_NEWNDUSEROPT);
94         NL_EVENT_RTM_NAME(LOCAL_QLOG_NL_EVENT);
95         NL_EVENT_RTM_NAME(LOCAL_NFLOG_PACKET);
96         default:
97             return NULL;
98     }
99 #undef NL_EVENT_RTM_NAME
100 }
101 
102 /*
103  * Checks that a binary NETLINK_ROUTE message is long enough for a payload of
104  * size bytes.
105  */
checkRtNetlinkLength(const struct nlmsghdr * nh,size_t size)106 static bool checkRtNetlinkLength(const struct nlmsghdr *nh, size_t size) {
107     if (nh->nlmsg_len < NLMSG_LENGTH(size)) {
108         SLOGE("Got a short %s message\n", rtMessageName(nh->nlmsg_type));
109         return false;
110     }
111     return true;
112 }
113 
114 /*
115  * Utility function to log errors.
116  */
maybeLogDuplicateAttribute(bool isDup,const char * attributeName,const char * messageName)117 static bool maybeLogDuplicateAttribute(bool isDup,
118                                        const char *attributeName,
119                                        const char *messageName) {
120     if (isDup) {
121         SLOGE("Multiple %s attributes in %s, ignoring\n", attributeName, messageName);
122         return true;
123     }
124     return false;
125 }
126 
127 /*
128  * Parse a RTM_NEWLINK message.
129  */
parseIfInfoMessage(const struct nlmsghdr * nh)130 bool NetlinkEvent::parseIfInfoMessage(const struct nlmsghdr *nh) {
131     struct ifinfomsg *ifi = (struct ifinfomsg *) NLMSG_DATA(nh);
132     if (!checkRtNetlinkLength(nh, sizeof(*ifi)))
133         return false;
134 
135     if ((ifi->ifi_flags & IFF_LOOPBACK) != 0) {
136         return false;
137     }
138 
139     int len = IFLA_PAYLOAD(nh);
140     struct rtattr *rta;
141     for (rta = IFLA_RTA(ifi); RTA_OK(rta, len); rta = RTA_NEXT(rta, len)) {
142         switch(rta->rta_type) {
143             case IFLA_IFNAME:
144                 asprintf(&mParams[0], "INTERFACE=%s", (char *) RTA_DATA(rta));
145                 mAction = (ifi->ifi_flags & IFF_LOWER_UP) ? Action::kLinkUp :
146                                                             Action::kLinkDown;
147                 mSubsystem = strdup("net");
148                 return true;
149         }
150     }
151 
152     return false;
153 }
154 
155 /*
156  * Parse a RTM_NEWADDR or RTM_DELADDR message.
157  */
parseIfAddrMessage(const struct nlmsghdr * nh)158 bool NetlinkEvent::parseIfAddrMessage(const struct nlmsghdr *nh) {
159     struct ifaddrmsg *ifaddr = (struct ifaddrmsg *) NLMSG_DATA(nh);
160     struct ifa_cacheinfo *cacheinfo = NULL;
161     char addrstr[INET6_ADDRSTRLEN] = "";
162     char ifname[IFNAMSIZ];
163 
164     if (!checkRtNetlinkLength(nh, sizeof(*ifaddr)))
165         return false;
166 
167     // Sanity check.
168     int type = nh->nlmsg_type;
169     if (type != RTM_NEWADDR && type != RTM_DELADDR) {
170         SLOGE("parseIfAddrMessage on incorrect message type 0x%x\n", type);
171         return false;
172     }
173 
174     // For log messages.
175     const char *msgtype = rtMessageName(type);
176 
177     struct rtattr *rta;
178     int len = IFA_PAYLOAD(nh);
179     for (rta = IFA_RTA(ifaddr); RTA_OK(rta, len); rta = RTA_NEXT(rta, len)) {
180         if (rta->rta_type == IFA_ADDRESS) {
181             // Only look at the first address, because we only support notifying
182             // one change at a time.
183             if (maybeLogDuplicateAttribute(*addrstr != '\0', "IFA_ADDRESS", msgtype))
184                 continue;
185 
186             // Convert the IP address to a string.
187             if (ifaddr->ifa_family == AF_INET) {
188                 struct in_addr *addr4 = (struct in_addr *) RTA_DATA(rta);
189                 if (RTA_PAYLOAD(rta) < sizeof(*addr4)) {
190                     SLOGE("Short IPv4 address (%zu bytes) in %s",
191                           RTA_PAYLOAD(rta), msgtype);
192                     continue;
193                 }
194                 inet_ntop(AF_INET, addr4, addrstr, sizeof(addrstr));
195             } else if (ifaddr->ifa_family == AF_INET6) {
196                 struct in6_addr *addr6 = (struct in6_addr *) RTA_DATA(rta);
197                 if (RTA_PAYLOAD(rta) < sizeof(*addr6)) {
198                     SLOGE("Short IPv6 address (%zu bytes) in %s",
199                           RTA_PAYLOAD(rta), msgtype);
200                     continue;
201                 }
202                 inet_ntop(AF_INET6, addr6, addrstr, sizeof(addrstr));
203             } else {
204                 SLOGE("Unknown address family %d\n", ifaddr->ifa_family);
205                 continue;
206             }
207 
208             // Find the interface name.
209             if (!if_indextoname(ifaddr->ifa_index, ifname)) {
210                 SLOGE("Unknown ifindex %d in %s", ifaddr->ifa_index, msgtype);
211                 return false;
212             }
213 
214         } else if (rta->rta_type == IFA_CACHEINFO) {
215             // Address lifetime information.
216             if (maybeLogDuplicateAttribute(cacheinfo, "IFA_CACHEINFO", msgtype))
217                 continue;
218 
219             if (RTA_PAYLOAD(rta) < sizeof(*cacheinfo)) {
220                 SLOGE("Short IFA_CACHEINFO (%zu vs. %zu bytes) in %s",
221                       RTA_PAYLOAD(rta), sizeof(cacheinfo), msgtype);
222                 continue;
223             }
224 
225             cacheinfo = (struct ifa_cacheinfo *) RTA_DATA(rta);
226         }
227     }
228 
229     if (addrstr[0] == '\0') {
230         SLOGE("No IFA_ADDRESS in %s\n", msgtype);
231         return false;
232     }
233 
234     // Fill in netlink event information.
235     mAction = (type == RTM_NEWADDR) ? Action::kAddressUpdated :
236                                       Action::kAddressRemoved;
237     mSubsystem = strdup("net");
238     asprintf(&mParams[0], "ADDRESS=%s/%d", addrstr,
239              ifaddr->ifa_prefixlen);
240     asprintf(&mParams[1], "INTERFACE=%s", ifname);
241     asprintf(&mParams[2], "FLAGS=%u", ifaddr->ifa_flags);
242     asprintf(&mParams[3], "SCOPE=%u", ifaddr->ifa_scope);
243 
244     if (cacheinfo) {
245         asprintf(&mParams[4], "PREFERRED=%u", cacheinfo->ifa_prefered);
246         asprintf(&mParams[5], "VALID=%u", cacheinfo->ifa_valid);
247         asprintf(&mParams[6], "CSTAMP=%u", cacheinfo->cstamp);
248         asprintf(&mParams[7], "TSTAMP=%u", cacheinfo->tstamp);
249     }
250 
251     return true;
252 }
253 
254 /*
255  * Parse a QLOG_NL_EVENT message.
256  */
parseUlogPacketMessage(const struct nlmsghdr * nh)257 bool NetlinkEvent::parseUlogPacketMessage(const struct nlmsghdr *nh) {
258     const char *devname;
259     ulog_packet_msg_t *pm = (ulog_packet_msg_t *) NLMSG_DATA(nh);
260     if (!checkRtNetlinkLength(nh, sizeof(*pm)))
261         return false;
262 
263     devname = pm->indev_name[0] ? pm->indev_name : pm->outdev_name;
264     asprintf(&mParams[0], "ALERT_NAME=%s", pm->prefix);
265     asprintf(&mParams[1], "INTERFACE=%s", devname);
266     mSubsystem = strdup("qlog");
267     mAction = Action::kChange;
268     return true;
269 }
270 
271 /*
272  * Parse a LOCAL_NFLOG_PACKET message.
273  */
parseNfPacketMessage(struct nlmsghdr * nh)274 bool NetlinkEvent::parseNfPacketMessage(struct nlmsghdr *nh) {
275     int uid = -1;
276     int len = 0;
277     char* raw = NULL;
278 
279     struct nlattr *uid_attr = nlmsg_find_attr(nh, sizeof(struct genlmsghdr), NFULA_UID);
280     if (uid_attr) {
281         uid = ntohl(nla_get_u32(uid_attr));
282     }
283 
284     struct nlattr *payload = nlmsg_find_attr(nh, sizeof(struct genlmsghdr), NFULA_PAYLOAD);
285     if (payload) {
286         /* First 256 bytes is plenty */
287         len = nla_len(payload);
288         if (len > 256) len = 256;
289         raw = (char*) nla_data(payload);
290     }
291 
292     char* hex = (char*) calloc(1, 5 + (len * 2));
293     strcpy(hex, "HEX=");
294     for (int i = 0; i < len; i++) {
295         hex[4 + (i * 2)] = "0123456789abcdef"[(raw[i] >> 4) & 0xf];
296         hex[5 + (i * 2)] = "0123456789abcdef"[raw[i] & 0xf];
297     }
298 
299     asprintf(&mParams[0], "UID=%d", uid);
300     mParams[1] = hex;
301     mSubsystem = strdup("strict");
302     mAction = Action::kChange;
303     return true;
304 }
305 
306 /*
307  * Parse a RTM_NEWROUTE or RTM_DELROUTE message.
308  */
parseRtMessage(const struct nlmsghdr * nh)309 bool NetlinkEvent::parseRtMessage(const struct nlmsghdr *nh) {
310     uint8_t type = nh->nlmsg_type;
311     const char *msgname = rtMessageName(type);
312 
313     // Sanity check.
314     if (type != RTM_NEWROUTE && type != RTM_DELROUTE) {
315         SLOGE("%s: incorrect message type %d (%s)\n", __func__, type, msgname);
316         return false;
317     }
318 
319     struct rtmsg *rtm = (struct rtmsg *) NLMSG_DATA(nh);
320     if (!checkRtNetlinkLength(nh, sizeof(*rtm)))
321         return false;
322 
323     if (// Ignore static routes we've set up ourselves.
324         (rtm->rtm_protocol != RTPROT_KERNEL &&
325          rtm->rtm_protocol != RTPROT_RA) ||
326         // We're only interested in global unicast routes.
327         (rtm->rtm_scope != RT_SCOPE_UNIVERSE) ||
328         (rtm->rtm_type != RTN_UNICAST) ||
329         // We don't support source routing.
330         (rtm->rtm_src_len != 0) ||
331         // Cloned routes aren't real routes.
332         (rtm->rtm_flags & RTM_F_CLONED)) {
333         return false;
334     }
335 
336     int family = rtm->rtm_family;
337     int prefixLength = rtm->rtm_dst_len;
338 
339     // Currently we only support: destination, (one) next hop, ifindex.
340     char dst[INET6_ADDRSTRLEN] = "";
341     char gw[INET6_ADDRSTRLEN] = "";
342     char dev[IFNAMSIZ] = "";
343 
344     size_t len = RTM_PAYLOAD(nh);
345     struct rtattr *rta;
346     for (rta = RTM_RTA(rtm); RTA_OK(rta, len); rta = RTA_NEXT(rta, len)) {
347         switch (rta->rta_type) {
348             case RTA_DST:
349                 if (maybeLogDuplicateAttribute(*dst, "RTA_DST", msgname))
350                     continue;
351                 if (!inet_ntop(family, RTA_DATA(rta), dst, sizeof(dst)))
352                     return false;
353                 continue;
354             case RTA_GATEWAY:
355                 if (maybeLogDuplicateAttribute(*gw, "RTA_GATEWAY", msgname))
356                     continue;
357                 if (!inet_ntop(family, RTA_DATA(rta), gw, sizeof(gw)))
358                     return false;
359                 continue;
360             case RTA_OIF:
361                 if (maybeLogDuplicateAttribute(*dev, "RTA_OIF", msgname))
362                     continue;
363                 if (!if_indextoname(* (int *) RTA_DATA(rta), dev))
364                     return false;
365             default:
366                 continue;
367         }
368     }
369 
370    // If there's no RTA_DST attribute, then:
371    // - If the prefix length is zero, it's the default route.
372    // - If the prefix length is nonzero, there's something we don't understand.
373    //   Ignore the event.
374    if (!*dst && !prefixLength) {
375         if (family == AF_INET) {
376             strncpy(dst, "0.0.0.0", sizeof(dst));
377         } else if (family == AF_INET6) {
378             strncpy(dst, "::", sizeof(dst));
379         }
380     }
381 
382     // A useful route must have a destination and at least either a gateway or
383     // an interface.
384     if (!*dst || (!*gw && !*dev))
385         return false;
386 
387     // Fill in netlink event information.
388     mAction = (type == RTM_NEWROUTE) ? Action::kRouteUpdated :
389                                        Action::kRouteRemoved;
390     mSubsystem = strdup("net");
391     asprintf(&mParams[0], "ROUTE=%s/%d", dst, prefixLength);
392     asprintf(&mParams[1], "GATEWAY=%s", (*gw) ? gw : "");
393     asprintf(&mParams[2], "INTERFACE=%s", (*dev) ? dev : "");
394 
395     return true;
396 }
397 
398 /*
399  * Parse a RTM_NEWNDUSEROPT message.
400  */
parseNdUserOptMessage(const struct nlmsghdr * nh)401 bool NetlinkEvent::parseNdUserOptMessage(const struct nlmsghdr *nh) {
402     struct nduseroptmsg *msg = (struct nduseroptmsg *) NLMSG_DATA(nh);
403     if (!checkRtNetlinkLength(nh, sizeof(*msg)))
404         return false;
405 
406     // Check the length is valid.
407     int len = NLMSG_PAYLOAD(nh, sizeof(*msg));
408     if (msg->nduseropt_opts_len > len) {
409         SLOGE("RTM_NEWNDUSEROPT invalid length %d > %d\n",
410               msg->nduseropt_opts_len, len);
411         return false;
412     }
413     len = msg->nduseropt_opts_len;
414 
415     // Check address family and packet type.
416     if (msg->nduseropt_family != AF_INET6) {
417         SLOGE("RTM_NEWNDUSEROPT message for unknown family %d\n",
418               msg->nduseropt_family);
419         return false;
420     }
421 
422     if (msg->nduseropt_icmp_type != ND_ROUTER_ADVERT ||
423         msg->nduseropt_icmp_code != 0) {
424         SLOGE("RTM_NEWNDUSEROPT message for unknown ICMPv6 type/code %d/%d\n",
425               msg->nduseropt_icmp_type, msg->nduseropt_icmp_code);
426         return false;
427     }
428 
429     // Find the interface name.
430     char ifname[IFNAMSIZ];
431     if (!if_indextoname(msg->nduseropt_ifindex, ifname)) {
432         SLOGE("RTM_NEWNDUSEROPT on unknown ifindex %d\n",
433               msg->nduseropt_ifindex);
434         return false;
435     }
436 
437     // The kernel sends a separate netlink message for each ND option in the RA.
438     // So only parse the first ND option in the message.
439     struct nd_opt_hdr *opthdr = (struct nd_opt_hdr *) (msg + 1);
440 
441     // The length is in multiples of 8 octets.
442     uint16_t optlen = opthdr->nd_opt_len;
443     if (optlen * 8 > len) {
444         SLOGE("Invalid option length %d > %d for ND option %d\n",
445               optlen * 8, len, opthdr->nd_opt_type);
446         return false;
447     }
448 
449     if (opthdr->nd_opt_type == ND_OPT_RDNSS) {
450         // DNS Servers (RFC 6106).
451         // Each address takes up 2*8 octets, and the header takes up 8 octets.
452         // So for a valid option with one or more addresses, optlen must be
453         // odd and greater than 1.
454         if ((optlen < 3) || !(optlen & 0x1)) {
455             SLOGE("Invalid optlen %d for RDNSS option\n", optlen);
456             return false;
457         }
458         const int numaddrs = (optlen - 1) / 2;
459 
460         // Find the lifetime.
461         struct nd_opt_rdnss *rndss_opt = (struct nd_opt_rdnss *) opthdr;
462         const uint32_t lifetime = ntohl(rndss_opt->nd_opt_rdnss_lifetime);
463 
464         // Construct "SERVERS=<comma-separated string of DNS addresses>".
465         static const char kServerTag[] = "SERVERS=";
466         static const size_t kTagLength = strlen(kServerTag);
467         // Reserve sufficient space for an IPv6 link-local address: all but the
468         // last address are followed by ','; the last is followed by '\0'.
469         static const size_t kMaxSingleAddressLength =
470                 INET6_ADDRSTRLEN + strlen("%") + IFNAMSIZ + strlen(",");
471         const size_t bufsize = kTagLength + numaddrs * kMaxSingleAddressLength;
472         char *buf = (char *) malloc(bufsize);
473         if (!buf) {
474             SLOGE("RDNSS option: out of memory\n");
475             return false;
476         }
477         strcpy(buf, kServerTag);
478         size_t pos = kTagLength;
479 
480         struct in6_addr *addrs = (struct in6_addr *) (rndss_opt + 1);
481         for (int i = 0; i < numaddrs; i++) {
482             if (i > 0) {
483                 buf[pos++] = ',';
484             }
485             inet_ntop(AF_INET6, addrs + i, buf + pos, bufsize - pos);
486             pos += strlen(buf + pos);
487             if (IN6_IS_ADDR_LINKLOCAL(addrs + i)) {
488                 buf[pos++] = '%';
489                 pos += strlcpy(buf + pos, ifname, bufsize - pos);
490             }
491         }
492         buf[pos] = '\0';
493 
494         mAction = Action::kRdnss;
495         mSubsystem = strdup("net");
496         asprintf(&mParams[0], "INTERFACE=%s", ifname);
497         asprintf(&mParams[1], "LIFETIME=%u", lifetime);
498         mParams[2] = buf;
499     } else {
500         SLOGD("Unknown ND option type %d\n", opthdr->nd_opt_type);
501         return false;
502     }
503 
504     return true;
505 }
506 
507 /*
508  * Parse a binary message from a NETLINK_ROUTE netlink socket.
509  *
510  * Note that this function can only parse one message, because the message's
511  * content has to be stored in the class's member variables (mAction,
512  * mSubsystem, etc.). Invalid or unrecognized messages are skipped, but if
513  * there are multiple valid messages in the buffer, only the first one will be
514  * returned.
515  *
516  * TODO: consider only ever looking at the first message.
517  */
parseBinaryNetlinkMessage(char * buffer,int size)518 bool NetlinkEvent::parseBinaryNetlinkMessage(char *buffer, int size) {
519     struct nlmsghdr *nh;
520 
521     for (nh = (struct nlmsghdr *) buffer;
522          NLMSG_OK(nh, (unsigned) size) && (nh->nlmsg_type != NLMSG_DONE);
523          nh = NLMSG_NEXT(nh, size)) {
524 
525         if (!rtMessageName(nh->nlmsg_type)) {
526             SLOGD("Unexpected netlink message type %d\n", nh->nlmsg_type);
527             continue;
528         }
529 
530         if (nh->nlmsg_type == RTM_NEWLINK) {
531             if (parseIfInfoMessage(nh))
532                 return true;
533 
534         } else if (nh->nlmsg_type == LOCAL_QLOG_NL_EVENT) {
535             if (parseUlogPacketMessage(nh))
536                 return true;
537 
538         } else if (nh->nlmsg_type == RTM_NEWADDR ||
539                    nh->nlmsg_type == RTM_DELADDR) {
540             if (parseIfAddrMessage(nh))
541                 return true;
542 
543         } else if (nh->nlmsg_type == RTM_NEWROUTE ||
544                    nh->nlmsg_type == RTM_DELROUTE) {
545             if (parseRtMessage(nh))
546                 return true;
547 
548         } else if (nh->nlmsg_type == RTM_NEWNDUSEROPT) {
549             if (parseNdUserOptMessage(nh))
550                 return true;
551 
552         } else if (nh->nlmsg_type == LOCAL_NFLOG_PACKET) {
553             if (parseNfPacketMessage(nh))
554                 return true;
555 
556         }
557     }
558 
559     return false;
560 }
561 
562 /* If the string between 'str' and 'end' begins with 'prefixlen' characters
563  * from the 'prefix' array, then return 'str + prefixlen', otherwise return
564  * NULL.
565  */
566 static const char*
has_prefix(const char * str,const char * end,const char * prefix,size_t prefixlen)567 has_prefix(const char* str, const char* end, const char* prefix, size_t prefixlen)
568 {
569     if ((end-str) >= (ptrdiff_t)prefixlen && !memcmp(str, prefix, prefixlen))
570         return str + prefixlen;
571     else
572         return NULL;
573 }
574 
575 /* Same as strlen(x) for constant string literals ONLY */
576 #define CONST_STRLEN(x)  (sizeof(x)-1)
577 
578 /* Convenience macro to call has_prefix with a constant string literal  */
579 #define HAS_CONST_PREFIX(str,end,prefix)  has_prefix((str),(end),prefix,CONST_STRLEN(prefix))
580 
581 
582 /*
583  * Parse an ASCII-formatted message from a NETLINK_KOBJECT_UEVENT
584  * netlink socket.
585  */
parseAsciiNetlinkMessage(char * buffer,int size)586 bool NetlinkEvent::parseAsciiNetlinkMessage(char *buffer, int size) {
587     const char *s = buffer;
588     const char *end;
589     int param_idx = 0;
590     int first = 1;
591 
592     if (size == 0)
593         return false;
594 
595     /* Ensure the buffer is zero-terminated, the code below depends on this */
596     buffer[size-1] = '\0';
597 
598     end = s + size;
599     while (s < end) {
600         if (first) {
601             const char *p;
602             /* buffer is 0-terminated, no need to check p < end */
603             for (p = s; *p != '@'; p++) {
604                 if (!*p) { /* no '@', should not happen */
605                     return false;
606                 }
607             }
608             mPath = strdup(p+1);
609             first = 0;
610         } else {
611             const char* a;
612             if ((a = HAS_CONST_PREFIX(s, end, "ACTION=")) != NULL) {
613                 if (!strcmp(a, "add"))
614                     mAction = Action::kAdd;
615                 else if (!strcmp(a, "remove"))
616                     mAction = Action::kRemove;
617                 else if (!strcmp(a, "change"))
618                     mAction = Action::kChange;
619             } else if ((a = HAS_CONST_PREFIX(s, end, "SEQNUM=")) != NULL) {
620                 mSeq = atoi(a);
621             } else if ((a = HAS_CONST_PREFIX(s, end, "SUBSYSTEM=")) != NULL) {
622                 mSubsystem = strdup(a);
623             } else if (param_idx < NL_PARAMS_MAX) {
624                 mParams[param_idx++] = strdup(s);
625             }
626         }
627         s += strlen(s) + 1;
628     }
629     return true;
630 }
631 
decode(char * buffer,int size,int format)632 bool NetlinkEvent::decode(char *buffer, int size, int format) {
633     if (format == NetlinkListener::NETLINK_FORMAT_BINARY
634             || format == NetlinkListener::NETLINK_FORMAT_BINARY_UNICAST) {
635         return parseBinaryNetlinkMessage(buffer, size);
636     } else {
637         return parseAsciiNetlinkMessage(buffer, size);
638     }
639 }
640 
findParam(const char * paramName)641 const char *NetlinkEvent::findParam(const char *paramName) {
642     size_t len = strlen(paramName);
643     for (int i = 0; i < NL_PARAMS_MAX && mParams[i] != NULL; ++i) {
644         const char *ptr = mParams[i] + len;
645         if (!strncmp(mParams[i], paramName, len) && *ptr == '=')
646             return ++ptr;
647     }
648 
649     SLOGE("NetlinkEvent::FindParam(): Parameter '%s' not found", paramName);
650     return NULL;
651 }
652