From 2d0a8bf2a1fcdc3f8a810e75671a2556d099f622 Mon Sep 17 00:00:00 2001
From: Michael Tuexen <tuexen@fh-muenster.de>
Date: Sun, 22 Apr 2018 21:28:42 +0200
Subject: [PATCH] Don't rely on pcap_setdirection() for filtering.
MacOS does not support pcap_setdirection() for PCAP_D_OUT.
Instead use only a single pcap handle (as it was originally) and
add a capture filter to only filter the packets in the expected
direction.
Only packets sent by the machine under test needs to be captured.
---
gtests/net/packetdrill/netdev.c | 4 +
gtests/net/packetdrill/packet_socket_pcap.c | 137 ++++++++------------
2 files changed, 56 insertions(+), 85 deletions(-)
diff --git a/gtests/net/packetdrill/netdev.c b/gtests/net/packetdrill/netdev.c
index d8bcd366..14996281 100644
--- a/gtests/net/packetdrill/netdev.c
+++ b/gtests/net/packetdrill/netdev.c
@@ -403,6 +403,10 @@ struct netdev *local_netdev_new(struct config *config)
route_traffic_to_device(config, netdev);
netdev->psock = packet_socket_new(netdev->name);
+ /* Make sure we only see packets from the machine under test. */
+ packet_socket_set_filter(netdev->psock,
+ NULL,
+ &config->live_local_ip); /* client IP */
return (struct netdev *)netdev;
}
diff --git a/gtests/net/packetdrill/packet_socket_pcap.c b/gtests/net/packetdrill/packet_socket_pcap.c
index d609067e..97d42587 100644
--- a/gtests/net/packetdrill/packet_socket_pcap.c
+++ b/gtests/net/packetdrill/packet_socket_pcap.c
@@ -47,9 +47,8 @@
struct packet_socket {
char *name; /* malloc-allocated copy of interface name */
- pcap_t *pcap_in; /* handle for sniffing incoming packets */
- pcap_t *pcap_out; /* handle for sniffing outgoing packets */
- /* also used for sending packets */
+ pcap_t *pcap; /* handle for sniffing packets sent by the SUT */
+ /* also used for sending packets */
char pcap_error[PCAP_ERRBUF_SIZE]; /* for libpcap errors */
int pcap_offset; /* offset of packet data in pcap buffer */
int data_link;
@@ -64,58 +63,30 @@ static inline s64 bpf_timeval_to_usecs(const struct bpf_timeval *tv)
}
#endif /* defined(__OpenBSD__) */
-/* Call pcap_perror() and then exit with a failure status code. */
-extern void die_pcap_perror(pcap_t *pcap, char *message)
-{
- pcap_perror(pcap, message);
-
- exit(EXIT_FAILURE);
-}
-
static void packet_socket_setup(struct packet_socket *psock)
{
+ int result;
+
DEBUGP("calling pcap_create() with %s\n", psock->name);
- psock->pcap_in = pcap_create(psock->name, psock->pcap_error);
- if (psock->pcap_in == NULL)
- die_pcap_perror(psock->pcap_in, "pcap_create");
- psock->pcap_out = pcap_create(psock->name, psock->pcap_error);
- if (psock->pcap_out == NULL)
- die_pcap_perror(psock->pcap_out, "pcap_create");
-
- if (pcap_set_snaplen(psock->pcap_in, PACKET_READ_BYTES) != 0)
- die_pcap_perror(psock->pcap_in, "pcap_set_snaplen");
- if (pcap_set_snaplen(psock->pcap_out, PACKET_READ_BYTES) != 0)
- die_pcap_perror(psock->pcap_out, "pcap_set_snaplen");
-
- /* By default libpcap with BPF waits until a read buffer fills
- * up before returning any packets. We use the immediate mode to
- * force the BPF device to return the first packet
- * immediately.
- * Enable this mode before activating the pcap handle.
- */
- if (pcap_set_immediate_mode(psock->pcap_in, 1) != 0)
- die_pcap_perror(psock->pcap_out, "pcap_set_immediate_mode");
- if (pcap_set_immediate_mode(psock->pcap_out, 1) != 0)
- die_pcap_perror(psock->pcap_out, "pcap_set_immediate_mode");
-
- if (pcap_activate(psock->pcap_in) != 0)
- die_pcap_perror(psock->pcap_in,
- "pcap_activate "
- "(OpenBSD: another process (tcpdump?) "
- "using bpf0?)");
- if (pcap_activate(psock->pcap_out) != 0)
- die_pcap_perror(psock->pcap_out,
- "pcap_activate "
- "(OpenBSD: another process (tcpdump?) "
- "using bpf0?)");
-
- if (pcap_setdirection(psock->pcap_in, PCAP_D_IN) != 0)
- die_pcap_perror(psock->pcap_in, "pcap_setdirection");
- if (pcap_setdirection(psock->pcap_out, PCAP_D_OUT) != 0)
- die_pcap_perror(psock->pcap_out, "pcap_setdirection");
-
- /* Find data link type. */
- psock->data_link = pcap_datalink(psock->pcap_in);
+ psock->pcap = pcap_create(psock->name, psock->pcap_error);
+ if (psock->pcap == NULL)
+ die("%s: %s\n", "pcap_create", psock->pcap_error);
+ /* The following two calls MUST be called before activating
+ * the handle. Then they are not failing. */
+ result = pcap_set_snaplen(psock->pcap, PACKET_READ_BYTES);
+ if (result != 0)
+ die("%s: %s\n", "pcap_set_snaplen", pcap_statustostr(result));
+ result = pcap_set_immediate_mode(psock->pcap, 1);
+ if (result != 0)
+ die("%s: %s\n", "pcap_set_immediate_mode", pcap_statustostr(result));
+ result = pcap_activate(psock->pcap);
+ if (result != 0) {
+ if (result == PCAP_WARNING || result == PCAP_ERROR)
+ die("%s: %s\n", "pcap_activate", pcap_geterr(psock->pcap));
+ else
+ die("%s: %s\n", "pcap_activate", pcap_statustostr(result));
+ }
+ psock->data_link = pcap_datalink(psock->pcap);
DEBUGP("data_link: %d\n", psock->data_link);
/* Based on the data_link type, calculate the offset of the
@@ -147,28 +118,28 @@ void packet_socket_set_filter(struct packet_socket *psock,
ip_to_string(client_live_ip, client_live_ip_string);
- asprintf(&filter_str,
- "ether src %02x:%02x:%02x:%02x:%02x:%02x and %s src %s",
- client_ether[0],
- client_ether[1],
- client_ether[2],
- client_ether[3],
- client_ether[4],
- client_ether[5],
- client_live_ip->address_family == AF_INET6 ? "ip6" : "ip",
- client_live_ip_string);
-
+ if (client_ether_addr != NULL)
+ asprintf(&filter_str,
+ "ether src %02x:%02x:%02x:%02x:%02x:%02x and %s src %s",
+ client_ether[0],
+ client_ether[1],
+ client_ether[2],
+ client_ether[3],
+ client_ether[4],
+ client_ether[5],
+ client_live_ip->address_family == AF_INET6 ? "ip6" : "ip",
+ client_live_ip_string);
+ else
+ asprintf(&filter_str,
+ "%s src %s",
+ client_live_ip->address_family == AF_INET6 ? "ip6" : "ip",
+ client_live_ip_string);
DEBUGP("setting BPF filter: %s\n", filter_str);
- if (pcap_compile(psock->pcap_in, &bpf_code, filter_str, 1, 0) != 0)
- die_pcap_perror(psock->pcap_in, "pcap_compile");
- if (pcap_setfilter(psock->pcap_in, &bpf_code) != 0)
- die_pcap_perror(psock->pcap_in, "pcap_setfilter");
- pcap_freecode(&bpf_code);
- if (pcap_compile(psock->pcap_out, &bpf_code, filter_str, 1, 0) != 0)
- die_pcap_perror(psock->pcap_out, "pcap_compile");
- if (pcap_setfilter(psock->pcap_out, &bpf_code) != 0)
- die_pcap_perror(psock->pcap_out, "pcap_setfilter");
+ if (pcap_compile(psock->pcap, &bpf_code, filter_str, 1, 0) != 0)
+ die("%s: %s\n", "pcap_compile", pcap_geterr(psock->pcap));
+ if (pcap_setfilter(psock->pcap, &bpf_code) != 0)
+ die("%s: %s\n", "pcap_setfilter", pcap_geterr(psock->pcap));
pcap_freecode(&bpf_code);
free(filter_str);
}
@@ -189,8 +160,7 @@ void packet_socket_free(struct packet_socket *psock)
if (psock->name != NULL)
free(psock->name);
- pcap_close(psock->pcap_in);
- pcap_close(psock->pcap_out);
+ pcap_close(psock->pcap);
memset(psock, 0, sizeof(*psock)); /* paranoia to catch bugs*/
free(psock);
@@ -204,7 +174,7 @@ int packet_socket_writev(struct packet_socket *psock,
*/
u8 *buf = NULL, *p = NULL;
- int len = 0, i = 0;
+ int len = 0, i = 0, result;
/* Calculate how much space we need. */
for (i = 0; i < iovcnt; ++i)
@@ -221,8 +191,11 @@ int packet_socket_writev(struct packet_socket *psock,
DEBUGP("calling pcap_inject with %d bytes\n", len);
- if (pcap_inject(psock->pcap_out, buf, len) != len)
- die_pcap_perror(psock->pcap_out, "pcap_inject");
+ result = pcap_inject(psock->pcap, buf, len);
+ if (result == -1)
+ die("%s: %s\n", "pcap_inject", pcap_geterr(psock->pcap));
+ if (result !=len)
+ die("%s: wrote %d bytes instead of %d\n", "pcap_inject", result, len);
free(buf);
return STATUS_OK;
@@ -235,18 +208,12 @@ int packet_socket_receive(struct packet_socket *psock,
int status = 0;
struct pcap_pkthdr *pkt_header = NULL;
const u8 *pkt_data = NULL;
- pcap_t *pcap;
struct ether_header *ether;
u32 address_family;
DEBUGP("calling pcap_next_ex() for direction %s\n",
direction == DIRECTION_INBOUND ? "inbound" : "outbound");
- if (direction == DIRECTION_INBOUND)
- pcap = psock->pcap_in;
- else
- pcap = psock->pcap_out;
-
/* Something about the way we're doing BIOCIMMEDIATE
* causes libpcap to return 0 if there's no packet
* yet, which forces us to spin in this loop until
@@ -257,13 +224,13 @@ int packet_socket_receive(struct packet_socket *psock,
* here. TODO(ncardwell): fix this.
*/
while (1) {
- status = pcap_next_ex(pcap, &pkt_header, &pkt_data);
+ status = pcap_next_ex(psock->pcap, &pkt_header, &pkt_data);
if (status == 1)
break; /* got a packet */
else if (status == 0)
return STATUS_ERR; /* no packet yet */
else if (status == -1)
- die_pcap_perror(pcap, "pcap_next_ex");
+ die("%s: %s\n", "pcap_inject", pcap_geterr(psock->pcap));
else if (status == -2)
die("pcap_next_ex: EOF in save file?!\n");
else
--
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