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