| 1 | /* Trivial libtrace program that prints the fields in the header for all |
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| 2 | * UDP packets in a trace. |
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| 3 | * |
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| 4 | * Designed to demonstrate the use of trace_get_transport() |
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| 5 | */ |
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| 6 | #include "libtrace.h" |
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| 7 | #include <stdio.h> |
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| 8 | #include <inttypes.h> |
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| 9 | #include <assert.h> |
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| 10 | #include <getopt.h> |
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| 11 | #include <arpa/inet.h> |
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| 12 | |
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| 13 | static void per_packet(libtrace_packet_t *packet) |
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| 14 | { |
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| 15 | uint8_t proto; |
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| 16 | uint32_t rem; |
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| 17 | void *transport = NULL; |
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| 18 | libtrace_udp_t *udp = NULL; |
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| 19 | |
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| 20 | /* OK, this is slightly tricky so pay attention. |
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| 21 | * |
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| 22 | * proto and rem are used as 'output' parameters here. What this |
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| 23 | * means is that their current values are ignored by the function |
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| 24 | * but they are updated to contain the protocol and amount of |
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| 25 | * payload remaining for the header that is being returned. |
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| 26 | * |
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| 27 | * We need to pass in the address of both these parameters, so |
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| 28 | * that they can be modified by the function. This is why there |
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| 29 | * is an '&' before both parameters. |
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| 30 | */ |
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| 31 | transport = trace_get_transport(packet, &proto, &rem); |
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| 32 | |
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| 33 | /* If there was no transport header, it can't be a UDP packet */ |
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| 34 | if (transport == NULL) |
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| 35 | return; |
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| 36 | |
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| 37 | /* Check if the protocol is UDP, using the defined value for UDP |
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| 38 | * that is defined in libtrace.h (search for libtrace_ipproto_t for |
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| 39 | * a full list) */ |
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| 40 | if (proto != TRACE_IPPROTO_UDP) |
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| 41 | return; |
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| 42 | |
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| 43 | /* One last check - make sure we have a full UDP header before |
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| 44 | * trying to grab fields out of it */ |
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| 45 | if (rem < sizeof(libtrace_udp_t)) |
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| 46 | return; |
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| 47 | |
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| 48 | /* Now, cast the returned header to the appropriate header type */ |
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| 49 | udp = (libtrace_udp_t *)transport; |
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| 50 | |
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| 51 | /* Dump each field to standard output. Be careful to byteswap any |
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| 52 | * fields that are larger than one byte, as these will be in network |
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| 53 | * byte order */ |
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| 54 | printf("UDP: source=%u dest=%u len=%u checksum=%u\n", |
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| 55 | ntohs(udp->source), ntohs(udp->dest), |
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| 56 | ntohs(udp->len), ntohs(udp->check)); |
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| 57 | } |
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| 58 | |
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| 59 | |
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| 60 | /* Due to the amount of error checking required in our main function, it |
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| 61 | * is a lot simpler and tidier to place all the calls to various libtrace |
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| 62 | * destroy functions into a separate function. |
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| 63 | */ |
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| 64 | static void libtrace_cleanup(libtrace_t *trace, libtrace_packet_t *packet) { |
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| 65 | |
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| 66 | /* It's very important to ensure that we aren't trying to destroy |
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| 67 | * a NULL structure, so each of the destroy calls will only occur |
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| 68 | * if the structure exists */ |
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| 69 | if (trace) |
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| 70 | trace_destroy(trace); |
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| 71 | |
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| 72 | if (packet) |
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| 73 | trace_destroy_packet(packet); |
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| 74 | |
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| 75 | } |
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| 76 | |
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| 77 | int main(int argc, char *argv[]) |
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| 78 | { |
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| 79 | /* This is essentially the same main function from readdemo.c */ |
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| 80 | |
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| 81 | libtrace_t *trace = NULL; |
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| 82 | libtrace_packet_t *packet = NULL; |
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| 83 | |
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| 84 | /* Ensure we have at least one argument after the program name */ |
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| 85 | if (argc < 2) { |
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| 86 | fprintf(stderr, "Usage: %s inputURI\n", argv[0]); |
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| 87 | return 1; |
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| 88 | } |
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| 89 | |
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| 90 | packet = trace_create_packet(); |
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| 91 | |
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| 92 | if (packet == NULL) { |
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| 93 | perror("Creating libtrace packet"); |
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| 94 | libtrace_cleanup(trace, packet); |
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| 95 | return 1; |
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| 96 | } |
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| 97 | |
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| 98 | trace = trace_create(argv[1]); |
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| 99 | |
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| 100 | if (trace_is_err(trace)) { |
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| 101 | trace_perror(trace,"Opening trace file"); |
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| 102 | libtrace_cleanup(trace, packet); |
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| 103 | return 1; |
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| 104 | } |
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| 105 | |
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| 106 | if (trace_start(trace) == -1) { |
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| 107 | trace_perror(trace,"Starting trace"); |
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| 108 | libtrace_cleanup(trace, packet); |
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| 109 | return 1; |
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| 110 | } |
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| 111 | |
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| 112 | |
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| 113 | while (trace_read_packet(trace,packet)>0) { |
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| 114 | per_packet(packet); |
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| 115 | } |
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| 116 | |
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| 117 | |
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| 118 | if (trace_is_err(trace)) { |
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| 119 | trace_perror(trace,"Reading packets"); |
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| 120 | libtrace_cleanup(trace, packet); |
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| 121 | return 1; |
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| 122 | } |
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| 123 | |
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| 124 | libtrace_cleanup(trace, packet); |
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| 125 | return 0; |
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| 126 | } |
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