GCC 9 complains:
nwfilter/nwfilter_dhcpsnoop.c: In function 'virNWFilterDHCPSnoopThread':
nwfilter/nwfilter_dhcpsnoop.c:1456:31: error: converting a packed 'virNWFilterSnoopEthHdrPtr' {aka 'struct _virNWFilterSnoopEthHdr *'} pointer (alignment 1) to 'const u_char *' {aka 'const unsigned char *'} (alignment 8) may result in an unaligned pointer value [-Werror=address-of-packed-member]
1456 | (const u_char **)&packet);
| ^
nwfilter/nwfilter_dhcpsnoop.c:183:8: note: defined here
183 | struct _virNWFilterSnoopEthHdr {
| ^~~~~~~~~~~~~~~~~~~~~~~
However it seems like there's more going on here than just an enhanced
GCC warning. The function pcap_next_ex is documented as:
the pointer pointed to by the
pkt_data argument is set to point to the data in the packet
We are passing a struct here rather than a pointer. I changed the
code to pass a pointer instead.
---
src/nwfilter/nwfilter_dhcpsnoop.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/src/nwfilter/nwfilter_dhcpsnoop.c b/src/nwfilter/nwfilter_dhcpsnoop.c
index 58f0057c3f..45873a542c 100644
--- a/src/nwfilter/nwfilter_dhcpsnoop.c
+++ b/src/nwfilter/nwfilter_dhcpsnoop.c
@@ -1335,7 +1335,7 @@ virNWFilterDHCPSnoopThread(void *req0)
{
virNWFilterSnoopReqPtr req = req0;
struct pcap_pkthdr *hdr;
- virNWFilterSnoopEthHdrPtr packet;
+ const virNWFilterSnoopEthHdrPtr *packetPtr;
int ifindex = 0;
int errcount = 0;
int tmp = -1, rv, n, pollTo;
@@ -1453,7 +1453,7 @@ virNWFilterDHCPSnoopThread(void *req0)
n--;
rv = pcap_next_ex(pcapConf[i].handle, &hdr,
- (const u_char **)&packet);
+ (const u_char **)&packetPtr);
if (rv < 0) {
/* error reading from socket */
@@ -1530,7 +1530,7 @@ virNWFilterDHCPSnoopThread(void *req0)
continue;
}
- if (virNWFilterSnoopDHCPDecodeJobSubmit(worker, packet,
+ if (virNWFilterSnoopDHCPDecodeJobSubmit(worker, *packetPtr,
hdr->caplen,
pcapConf[i].dir,
&pcapConf[i].qCtr) < 0) {
--
2.20.1
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