├── .travis.yml ├── COPYING ├── README.md └── nfqueue ├── libnfqueue1.go ├── nfq_cb.go ├── nfqueue.go ├── test_nfqueue └── test_nfqueue.go └── test_nfqueue_gopacket └── test_nfqueue.go /.travis.yml: -------------------------------------------------------------------------------- 1 | language: go 2 | 3 | go: 4 | - 1.6 5 | - tip 6 | install: 7 | - go get github.com/google/gopacket 8 | - go get github.com/google/gopacket/layers 9 | - go get github.com/chifflier/nfqueue-go/nfqueue 10 | before_install: 11 | - sudo apt-get -qq update 12 | - sudo apt-get install -y pkg-config libnfnetlink-dev libnetfilter-queue-dev 13 | -------------------------------------------------------------------------------- /COPYING: -------------------------------------------------------------------------------- 1 | GNU GENERAL PUBLIC LICENSE 2 | Version 2, June 1991 3 | 4 | Copyright (C) 1989, 1991 Free Software Foundation, Inc., 5 | 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA 6 | Everyone is permitted to copy and distribute verbatim copies 7 | of this license document, but changing it is not allowed. 8 | 9 | Preamble 10 | 11 | The licenses for most software are designed to take away your 12 | freedom to share and change it. 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Of course, the commands you use may 322 | be called something other than `show w' and `show c'; they could even be 323 | mouse-clicks or menu items--whatever suits your program. 324 | 325 | You should also get your employer (if you work as a programmer) or your 326 | school, if any, to sign a "copyright disclaimer" for the program, if 327 | necessary. Here is a sample; alter the names: 328 | 329 | Yoyodyne, Inc., hereby disclaims all copyright interest in the program 330 | `Gnomovision' (which makes passes at compilers) written by James Hacker. 331 | 332 | , 1 April 1989 333 | Ty Coon, President of Vice 334 | 335 | This General Public License does not permit incorporating your program into 336 | proprietary programs. If your program is a subroutine library, you may 337 | consider it more useful to permit linking proprietary applications with the 338 | library. If this is what you want to do, use the GNU Lesser General 339 | Public License instead of this License. 340 | -------------------------------------------------------------------------------- /README.md: -------------------------------------------------------------------------------- 1 | # nfqueue-go 2 | 3 | 4 | [![Build Status](https://travis-ci.org/chifflier/nfqueue-go.svg?branch=master)](https://travis-ci.org/chifflier/nfqueue-go) 5 | [![GoDoc](https://godoc.org/github.com/chifflier/nfqueue-go?status.svg)](https://godoc.org/github.com/chifflier/nfqueue-go/nfqueue) 6 | 7 | nfqueue-go is a wrapper library for 8 | [libnetfilter-queue](http://www.netfilter.org/projects/libnetfilter_queue/). The goal is to provide a library to gain access to packets queued by the kernel packet filter. 9 | 10 | It is important to note that these bindings will not follow blindly libnetfilter_queue API. For ex., some higher-level wrappers will be provided for the open/bind/create mechanism (using one function call instead of three). 11 | 12 | **The API is not yet stable.** 13 | 14 | To use the library, a program must 15 | - open a queue 16 | - bind to a network family (`AF_PACKET` for IPv4) 17 | - provide a callback function, which will be automatically called when a packet is received. The callback must return a verdict 18 | - create the queue, providing the queue number (which must match the `--queue-num` from the iptables rules, see below 19 | - run a loop, waiting for events. The program should also provide a clean way to exit the loop (for ex on `SIGINT`) 20 | 21 | ## Using library 22 | 23 | ``` 24 | import "github.com/chifflier/nfqueue-go/nfqueue" 25 | ``` 26 | 27 | ## Example 28 | 29 | See [test_nfqueue](nfqueue/test_nfqueue/test_nfqueue.go) for a minimal example, and [test_nfqueue_gopacket](nfqueue/test_nfqueue_gopacket/test_nfqueue.go) for an example using the [gopacket](https://github.com/google/gopacket) library to decode the packets. 30 | 31 | ## IPtables 32 | 33 | You must add rules in netfilter to send packets to the userspace queue. 34 | The number of the queue (--queue-num option in netfilter) must match the 35 | number provided to create_queue(). 36 | 37 | Example of iptables rules: 38 | 39 | iptables -A OUTPUT --destination 1.2.3.4 -j NFQUEUE --queue-num 0 40 | 41 | Of course, you should be more restrictive, depending on your needs. 42 | 43 | ## Privileges 44 | 45 | nfqueue-go does not require root privileges, but needs to open a netlink socket and send/receive packets to the kernel. 46 | 47 | You have several options: 48 | - Use the CAP_NET_ADMIN capability in order to allow your application to receive from and to send packets to kernel-space: 49 | ```setcap 'cap_net_admin=+ep' /path/to/program``` 50 | - Run your program as `root` and drop privileges 51 | 52 | ## License 53 | 54 | This library is licensed under the GNU General Public License version 2, or (at your option) any later version. 55 | -------------------------------------------------------------------------------- /nfqueue/libnfqueue1.go: -------------------------------------------------------------------------------- 1 | // +build libnfqueue1 2 | 3 | package nfqueue 4 | 5 | // This file contains code specific to versions >= 1.0 of libnetfilter_queue 6 | 7 | /* 8 | #include 9 | #include 10 | #include 11 | #include 12 | #include 13 | */ 14 | import "C" 15 | 16 | import ( 17 | "log" 18 | "unsafe" 19 | ) 20 | 21 | // SetVerdictMark issues a verdict for a packet, but a mark can be set 22 | // 23 | // Every queued packet _must_ have a verdict specified by userspace. 24 | func (p *Payload) SetVerdictMark(verdict int, mark uint32) error { 25 | log.Printf("Setting verdict for packet %d: %d mark %lx\n",p.Id,verdict,mark) 26 | C.nfq_set_verdict2( 27 | p.c_qh, 28 | C.u_int32_t(p.Id), 29 | C.u_int32_t(verdict), 30 | C.u_int32_t(mark), 31 | 0,nil) 32 | return nil 33 | } 34 | 35 | // SetVerdictMarkModified issues a verdict for a packet, but replaces the 36 | // packet with the provided one, and a mark can be set. 37 | // 38 | // Every queued packet _must_ have a verdict specified by userspace. 39 | func (p *Payload) SetVerdictMarkModified(verdict int, mark uint32, data []byte) error { 40 | log.Printf("Setting verdict for NEW packet %d: %d mark %lx\n",p.Id,verdict,mark) 41 | C.nfq_set_verdict2( 42 | p.c_qh, 43 | C.u_int32_t(p.Id), 44 | C.u_int32_t(verdict), 45 | C.u_int32_t(mark), 46 | C.u_int32_t(len(data)), 47 | (*C.uchar)(unsafe.Pointer(&data[0])), 48 | ) 49 | return nil 50 | } 51 | -------------------------------------------------------------------------------- /nfqueue/nfq_cb.go: -------------------------------------------------------------------------------- 1 | package nfqueue 2 | 3 | import ( 4 | "unsafe" 5 | ) 6 | 7 | import "C" 8 | 9 | /* 10 | Cast argument to Queue* before calling the real callback 11 | 12 | Notes: 13 | - export cannot be done in the same file (nfqueue.go) else it 14 | fails to build (multiple definitions of C functions) 15 | See https://github.com/golang/go/issues/3497 16 | See https://github.com/golang/go/wiki/cgo 17 | - this cast is caused by the fact that cgo does not support 18 | exporting structs 19 | See https://github.com/golang/go/wiki/cgo 20 | 21 | This function must _nerver_ be called directly. 22 | */ 23 | /* 24 | BUG(GoCallbackWrapper): The return value from the Go callback is used as a 25 | verdict. This works, and avoids packets without verdict to be queued, but 26 | prevents using out-of-order replies. 27 | */ 28 | //export GoCallbackWrapper 29 | func GoCallbackWrapper(ptr_q *unsafe.Pointer, ptr_nfad *unsafe.Pointer) int { 30 | q := (*Queue)(unsafe.Pointer(ptr_q)) 31 | payload := build_payload(q.c_qh, ptr_nfad) 32 | return q.cb(payload) 33 | } 34 | 35 | 36 | -------------------------------------------------------------------------------- /nfqueue/nfqueue.go: -------------------------------------------------------------------------------- 1 | // Go bindings for the NFQUEUE netfilter target 2 | // libnetfilter_queue is a userspace library providing an API to access packets 3 | // that have been queued by the Linux kernel packet filter. 4 | // 5 | // This provides an easy way to filter packets from userspace, and use tools 6 | // or libraries that are not accessible from kernelspace. 7 | // 8 | // BUG(nfqueue): This package currently displays lots of debug information 9 | package nfqueue 10 | 11 | // XXX we should use something like 12 | // pkg-config --libs libnetfilter_queue 13 | 14 | // #cgo pkg-config: libnetfilter_queue 15 | /* 16 | #include 17 | #include 18 | #include 19 | #include 20 | #include 21 | #include 22 | 23 | extern int GoCallbackWrapper(void *data, void *nfad); 24 | static inline ssize_t recv_to(int sockfd, void *buf, size_t len, int flags, int to); 25 | 26 | int _process_loop(struct nfq_handle *h, 27 | int *fd, 28 | int flags, 29 | int max_count) { 30 | int rv; 31 | char buf[65535]; 32 | int count; 33 | 34 | count = 0; 35 | 36 | (*fd) = nfq_fd(h); 37 | if (fd < 0) { 38 | return -1; 39 | } 40 | 41 | //avoid ENOBUFS on read() operation, otherwise the while loop is interrupted. 42 | int opt = 1; 43 | rv = setsockopt(*fd, SOL_NETLINK, NETLINK_NO_ENOBUFS, &opt, sizeof(int)); 44 | if (rv == -1) { 45 | return -1; 46 | } 47 | 48 | while (h && *fd != -1) { 49 | rv = recv_to(*fd, buf, sizeof(buf), flags, 500); 50 | if (rv > 0) { 51 | nfq_handle_packet(h, buf, rv); 52 | count++; 53 | if (max_count > 0 && count >= max_count) { 54 | break; 55 | } 56 | } else if (rv < 0){ 57 | return rv; 58 | } 59 | } 60 | return count; 61 | } 62 | 63 | void _stop_loop(int *fd) { 64 | (*fd) = -1; 65 | } 66 | 67 | // recv with timeout using select 68 | static inline ssize_t recv_to(int sockfd, void *buf, size_t len, int flags, int to) { 69 | int rv; 70 | ssize_t result; 71 | fd_set readset; 72 | 73 | // Initialize timeval struct 74 | struct timeval timeout; 75 | timeout.tv_sec = 0; 76 | timeout.tv_usec = to * 1000; 77 | 78 | // Initialize socket set 79 | FD_ZERO(&readset); 80 | FD_SET(sockfd, &readset); 81 | 82 | rv = select(sockfd+1, &readset, (fd_set *) 0, (fd_set *) 0, &timeout); 83 | // Check status 84 | if (rv < 0) { 85 | return -1; 86 | } else if (rv > 0 && FD_ISSET(sockfd, &readset)) { 87 | // Receive (ensure that the socket is set to non blocking mode!) 88 | result = recv(sockfd, buf, len, flags); 89 | return result; 90 | } 91 | 92 | return 0; 93 | } 94 | 95 | int c_nfq_cb(struct nfq_q_handle *qh, 96 | struct nfgenmsg *nfmsg, 97 | struct nfq_data *nfad, void *data) { 98 | return GoCallbackWrapper(data, nfad); 99 | } 100 | 101 | // wrap nfq_get_payload so cgo always have the same prototype 102 | // (libnetfilter_queue 0.17 uses a signed char) 103 | static int _c_get_payload (struct nfq_data *nfad, unsigned char **data) 104 | { 105 | return nfq_get_payload (nfad, data); 106 | } 107 | */ 108 | import "C" 109 | 110 | import ( 111 | "errors" 112 | "log" 113 | "unsafe" 114 | ) 115 | 116 | var ErrNotInitialized = errors.New("nfqueue: queue not initialized") 117 | var ErrOpenFailed = errors.New("nfqueue: open failed") 118 | var ErrRuntime = errors.New("nfqueue: runtime error") 119 | 120 | var NF_DROP = C.NF_DROP 121 | var NF_ACCEPT = C.NF_ACCEPT 122 | var NF_QUEUE = C.NF_QUEUE 123 | var NF_REPEAT = C.NF_REPEAT 124 | var NF_STOP = C.NF_STOP 125 | 126 | var NFQNL_COPY_NONE uint8 = C.NFQNL_COPY_NONE 127 | var NFQNL_COPY_META uint8 = C.NFQNL_COPY_META 128 | var NFQNL_COPY_PACKET uint8 = C.NFQNL_COPY_PACKET 129 | 130 | // Prototype for a NFQUEUE callback. 131 | // The callback receives the NFQUEUE ID of the packet, and 132 | // the packet payload. 133 | // Packet data start from the IP layer (ethernet information are not included). 134 | // It must return the verdict for the packet. 135 | type Callback func(*Payload) int 136 | 137 | // Queue is an opaque structure describing a connection to a kernel NFQUEUE, 138 | // and the associated Go callback. 139 | type Queue struct { 140 | c_h (*C.struct_nfq_handle) 141 | c_qh (*C.struct_nfq_q_handle) 142 | c_fd (*C.int) 143 | 144 | cb Callback 145 | } 146 | 147 | // Init creates a netfilter queue which can be used to receive packets 148 | // from the kernel. 149 | func (q *Queue) Init() error { 150 | log.Println("Opening queue") 151 | q.c_h = C.nfq_open() 152 | if (q.c_h == nil) { 153 | log.Println("nfq_open failed") 154 | return ErrOpenFailed 155 | } 156 | q.c_fd = (*C.int)(C.malloc(C.sizeof_int)) 157 | return nil 158 | } 159 | 160 | // SetCallback sets the callback function, fired when a packet is received. 161 | func (q *Queue) SetCallback(cb Callback) error { 162 | q.cb = cb 163 | return nil 164 | } 165 | 166 | func (q *Queue) Close() { 167 | if (q.c_h != nil) { 168 | log.Println("Closing queue") 169 | C.nfq_close(q.c_h) 170 | q.c_h = nil 171 | } 172 | C.free(unsafe.Pointer(q.c_fd)) 173 | } 174 | 175 | // Bind binds a Queue to a given protocol family. 176 | // 177 | // Usually, the family is syscall.AF_INET for IPv4, and syscall.AF_INET6 for IPv6 178 | func (q *Queue) Bind(af_family int) error { 179 | if (q.c_h == nil) { 180 | return ErrNotInitialized 181 | } 182 | log.Println("Binding to selected family") 183 | /* Errors in nfq_bind_pf are non-fatal ... 184 | * This function just tells the kernel that nfnetlink_queue is 185 | * the chosen module to queue packets to userspace. 186 | */ 187 | _ = C.nfq_bind_pf(q.c_h,C.u_int16_t(af_family)) 188 | return nil 189 | } 190 | 191 | // Unbind a queue from the given protocol family. 192 | // 193 | // Note that errors from this function can usually be ignored. 194 | func (q *Queue) Unbind(af_family int) error { 195 | if (q.c_h == nil) { 196 | return ErrNotInitialized 197 | } 198 | log.Println("Unbinding to selected family") 199 | rc := C.nfq_unbind_pf(q.c_h,C.u_int16_t(af_family)) 200 | if (rc < 0) { 201 | log.Println("nfq_unbind_pf failed") 202 | return ErrRuntime 203 | } 204 | return nil 205 | } 206 | 207 | // Create a new queue handle 208 | // 209 | // The queue must be initialized (using Init) and bound (using Bind), and 210 | // a callback function must be set (using SetCallback). 211 | func (q *Queue) CreateQueue(queue_num int) error { 212 | if (q.c_h == nil) { 213 | return ErrNotInitialized 214 | } 215 | if (q.cb == nil) { 216 | return ErrNotInitialized 217 | } 218 | log.Println("Creating queue") 219 | q.c_qh = C.nfq_create_queue(q.c_h,C.u_int16_t(queue_num),(*C.nfq_callback)(C.c_nfq_cb),unsafe.Pointer(q)) 220 | if (q.c_qh == nil) { 221 | log.Println("nfq_create_queue failed") 222 | return ErrRuntime 223 | } 224 | // Default mode 225 | C.nfq_set_mode(q.c_qh,C.NFQNL_COPY_PACKET,0xffff) 226 | return nil 227 | } 228 | 229 | // Destroy a queue handle 230 | // 231 | // This also unbind from the nfqueue handler, so you don't have to call Unbind() 232 | // Note that errors from this function can usually be ignored. 233 | func (q *Queue) DestroyQueue() error { 234 | if (q.c_qh == nil) { 235 | return ErrNotInitialized 236 | } 237 | log.Println("Destroy queue") 238 | rc := C.nfq_destroy_queue(q.c_qh) 239 | if (rc < 0) { 240 | log.Println("nfq_destroy_queue failed") 241 | return ErrRuntime 242 | } 243 | q.c_qh = nil 244 | return nil 245 | } 246 | 247 | // SetMode sets the amount of packet data that nfqueue copies to userspace 248 | // 249 | // Default mode is NFQNL_COPY_PACKET 250 | func (q *Queue) SetMode(mode uint8) error { 251 | if (q.c_h == nil) { 252 | return ErrNotInitialized 253 | } 254 | if (q.c_qh == nil) { 255 | return ErrNotInitialized 256 | } 257 | C.nfq_set_mode(q.c_qh,C.u_int8_t(mode),0xffff) 258 | return nil 259 | } 260 | 261 | // SetQueueMaxLen fixes the number of packets the kernel will store before internally before dropping upcoming packets 262 | func (q *Queue) SetQueueMaxLen(maxlen uint32) error { 263 | if (q.c_h == nil) { 264 | return ErrNotInitialized 265 | } 266 | if (q.c_qh == nil) { 267 | return ErrNotInitialized 268 | } 269 | C.nfq_set_queue_maxlen(q.c_qh,C.u_int32_t(maxlen)) 270 | return nil 271 | } 272 | 273 | // Main loop: Loop starts a loop, receiving kernel events 274 | // and processing packets using the callback function. 275 | func (q *Queue) Loop() error { 276 | if (q.c_h == nil) { 277 | return ErrNotInitialized 278 | } 279 | if (q.c_qh == nil) { 280 | return ErrNotInitialized 281 | } 282 | if (q.cb == nil) { 283 | return ErrNotInitialized 284 | } 285 | 286 | log.Println("Start Loop") 287 | ret := C._process_loop(q.c_h, q.c_fd, 0, -1) 288 | if ret < 0 { 289 | return ErrRuntime 290 | } 291 | return nil 292 | } 293 | 294 | func (q *Queue) StopLoop() { 295 | log.Println("Stop Loop") 296 | C._stop_loop(q.c_fd) 297 | } 298 | 299 | // Payload is a structure describing a packet received from the kernel 300 | type Payload struct { 301 | c_qh (*C.struct_nfq_q_handle) 302 | nfad *C.struct_nfq_data 303 | 304 | // NFQueue ID of the packet 305 | Id uint32 306 | // Packet data 307 | Data []byte 308 | } 309 | 310 | func build_payload(c_qh *C.struct_nfq_q_handle, ptr_nfad *unsafe.Pointer) *Payload { 311 | var payload_data *C.uchar 312 | var data []byte 313 | 314 | nfad := (*C.struct_nfq_data)(unsafe.Pointer(ptr_nfad)) 315 | 316 | ph := C.nfq_get_msg_packet_hdr(nfad) 317 | id := C.ntohl(C.uint32_t(ph.packet_id)) 318 | payload_len := C._c_get_payload(nfad, &payload_data) 319 | if (payload_len >= 0) { 320 | data = C.GoBytes(unsafe.Pointer(payload_data), C.int(payload_len)) 321 | } 322 | 323 | p := new(Payload) 324 | p.c_qh = c_qh 325 | p.nfad = nfad 326 | p.Id = uint32(id) 327 | p.Data = data 328 | 329 | return p 330 | } 331 | 332 | // SetVerdict issues a verdict for a packet. 333 | // 334 | // Every queued packet _must_ have a verdict specified by userspace. 335 | func (p *Payload) SetVerdict(verdict int) error { 336 | log.Printf("Setting verdict for packet %d: %d\n",p.Id,verdict) 337 | C.nfq_set_verdict(p.c_qh,C.u_int32_t(p.Id),C.u_int32_t(verdict),0,nil) 338 | return nil 339 | } 340 | 341 | // SetVerdictModified issues a verdict for a packet, but replaces the packet 342 | // with the provided one. 343 | // 344 | // Every queued packet _must_ have a verdict specified by userspace. 345 | func (p *Payload) SetVerdictModified(verdict int, data []byte) error { 346 | log.Printf("Setting verdict for NEW packet %d: %d\n",p.Id,verdict) 347 | C.nfq_set_verdict( 348 | p.c_qh, 349 | C.u_int32_t(p.Id), 350 | C.u_int32_t(verdict), 351 | C.u_int32_t(len(data)), 352 | (*C.uchar)(unsafe.Pointer(&data[0])), 353 | ) 354 | return nil 355 | } 356 | 357 | // Returns the packet mark 358 | func (p *Payload) GetNFMark() uint32 { 359 | return uint32(C.nfq_get_nfmark(p.nfad)) 360 | } 361 | 362 | // Returns the interface that the packet was received through 363 | func (p *Payload) GetInDev() uint32 { 364 | return uint32(C.nfq_get_indev(p.nfad)) 365 | } 366 | 367 | // Returns the interface that the packet will be routed out 368 | func (p *Payload) GetOutDev() uint32 { 369 | return uint32(C.nfq_get_outdev(p.nfad)) 370 | } 371 | 372 | // Returns the physical interface that the packet was received through 373 | func (p *Payload) GetPhysInDev() uint32 { 374 | return uint32(C.nfq_get_physindev(p.nfad)) 375 | } 376 | 377 | // Returns the physical interface that the packet will be routed out 378 | func (p *Payload) GetPhysOutDev() uint32 { 379 | return uint32(C.nfq_get_physoutdev(p.nfad)) 380 | } 381 | -------------------------------------------------------------------------------- /nfqueue/test_nfqueue/test_nfqueue.go: -------------------------------------------------------------------------------- 1 | package main 2 | 3 | import ( 4 | "encoding/hex" 5 | "fmt" 6 | "github.com/chifflier/nfqueue-go/nfqueue" 7 | "os" 8 | "os/signal" 9 | "syscall" 10 | ) 11 | 12 | func real_callback(payload *nfqueue.Payload) int { 13 | fmt.Println("Real callback") 14 | fmt.Printf(" id: %d\n", payload.Id) 15 | fmt.Printf(" mark: %d\n", payload.GetNFMark()) 16 | fmt.Printf(" in %d out %d\n", payload.GetInDev(), payload.GetOutDev()) 17 | fmt.Printf(" Φin %d Φout %d\n", payload.GetPhysInDev(), payload.GetPhysOutDev()) 18 | fmt.Println(hex.Dump(payload.Data)) 19 | fmt.Println("-- ") 20 | payload.SetVerdict(nfqueue.NF_ACCEPT) 21 | return 0 22 | } 23 | 24 | func main() { 25 | q := new(nfqueue.Queue) 26 | 27 | q.SetCallback(real_callback) 28 | 29 | q.Init() 30 | defer q.Close() 31 | 32 | q.Unbind(syscall.AF_INET) 33 | q.Bind(syscall.AF_INET) 34 | 35 | q.CreateQueue(0) 36 | q.SetMode(nfqueue.NFQNL_COPY_PACKET) 37 | 38 | c := make(chan os.Signal, 1) 39 | signal.Notify(c, os.Interrupt) 40 | go func(){ 41 | for sig := range c { 42 | // sig is a ^C, handle it 43 | _ = sig 44 | q.StopLoop() 45 | } 46 | }() 47 | 48 | // XXX Drop privileges here 49 | 50 | q.Loop() 51 | q.DestroyQueue() 52 | q.Close() 53 | os.Exit(0) 54 | } 55 | -------------------------------------------------------------------------------- /nfqueue/test_nfqueue_gopacket/test_nfqueue.go: -------------------------------------------------------------------------------- 1 | package main 2 | 3 | import ( 4 | "encoding/hex" 5 | "fmt" 6 | "github.com/chifflier/nfqueue-go/nfqueue" 7 | "os" 8 | "os/signal" 9 | "syscall" 10 | 11 | "github.com/google/gopacket" 12 | "github.com/google/gopacket/layers" 13 | ) 14 | 15 | func real_callback(payload *nfqueue.Payload) int { 16 | fmt.Println("Real callback") 17 | fmt.Printf(" id: %d\n", payload.Id) 18 | fmt.Println(hex.Dump(payload.Data)) 19 | // Decode a packet 20 | packet := gopacket.NewPacket(payload.Data, layers.LayerTypeIPv4, gopacket.Default) 21 | // Get the TCP layer from this packet 22 | if tcpLayer := packet.Layer(layers.LayerTypeTCP); tcpLayer != nil { 23 | fmt.Println("This is a TCP packet!") 24 | // Get actual TCP data from this layer 25 | tcp, _ := tcpLayer.(*layers.TCP) 26 | fmt.Printf("From src port %d to dst port %d\n", tcp.SrcPort, tcp.DstPort) 27 | } 28 | // Iterate over all layers, printing out each layer type 29 | for _, layer := range packet.Layers() { 30 | fmt.Println("PACKET LAYER:", layer.LayerType()) 31 | fmt.Println(gopacket.LayerDump(layer)) 32 | } 33 | fmt.Println("-- ") 34 | payload.SetVerdict(nfqueue.NF_ACCEPT) 35 | return 0 36 | } 37 | 38 | func main() { 39 | q := new(nfqueue.Queue) 40 | 41 | q.SetCallback(real_callback) 42 | 43 | q.Init() 44 | 45 | q.Unbind(syscall.AF_INET) 46 | q.Bind(syscall.AF_INET) 47 | 48 | q.CreateQueue(0) 49 | 50 | c := make(chan os.Signal, 1) 51 | signal.Notify(c, os.Interrupt) 52 | go func(){ 53 | for sig := range c { 54 | // sig is a ^C, handle it 55 | _ = sig 56 | q.StopLoop() 57 | } 58 | }() 59 | 60 | // XXX Drop privileges here 61 | 62 | q.Loop() 63 | q.DestroyQueue() 64 | q.Close() 65 | os.Exit(0) 66 | } 67 | --------------------------------------------------------------------------------