Fix a number of benign compiler warnings on Linux/GCC (#805)

src/recv.c:103:17: warning: ‘static’ is not at beginning of declaration [-Wold-style-declaration]
  103 |                 const static uint32_t available_space = sizeof(fake_eth_hdr) - sizeof(struct ether_header);
      |                 ^~~~~

src/if-netmap-linux.c: In function ‘fetch_stats64’:
src/if-netmap-linux.c:94:18: warning: ISO C99 doesn’t support unnamed structs/unions [-Wpedantic]
   94 |                 };
      |                  ^

src/probe_modules/packet.h: In function ‘check_dst_port’:
src/probe_modules/packet.h:162:37: warning: suggest parentheses around comparison in operand of ‘^’ -Wparentheses]
  162 |                 return (to_validate <= max ^ to_validate >= min);
      |                         ~~~~~~~~~~~~^~~~~~

src/probe_modules/packet.c: In function ‘set_timestamp_option_with_nops’:
src/probe_modules/packet.c:178:24: warning: implicit declaration of function ‘time’ [-Wimplicit-function-declaration]
  178 |         uint32_t now = time(NULL);
      |                        ^~~~
src/probe_modules/packet.c:178:24: warning: nested extern declaration of ‘time’ [-Wnested-externs]
  178 |         uint32_t now = time(NULL);
      |                        ^~~~

src/if-netmap-linux.c

@@ -91,15 +91,15 @@ fetch_stats64(struct rtnl_link_stats64 *rtlstats64, char const *ifname, int nlrt
 			struct {
 				struct nlmsgerr nlerr;
 			} err;
-		};
+		} u;
 	} nlresp;
-	_Static_assert(sizeof(nlresp.ans) >= sizeof(nlresp.err));
-	static const size_t ans_size = offsetof(struct nlresp, ans) + sizeof(nlresp.ans);
-	static const size_t err_size = offsetof(struct nlresp, err) + sizeof(nlresp.err);
+	_Static_assert(sizeof(nlresp.u.ans) >= sizeof(nlresp.u.err));
+	static const size_t ans_size = offsetof(struct nlresp, u.ans) + sizeof(nlresp.u.ans);
+	static const size_t err_size = offsetof(struct nlresp, u.err) + sizeof(nlresp.u.err);
 
 	memset(iov, 0, sizeof(iov));
 	iov[0].iov_base = (void *)&nlresp;
-	iov[0].iov_len = offsetof(struct nlresp, ans.rtlstats64);
+	iov[0].iov_len = offsetof(struct nlresp, u.ans.rtlstats64);
 	iov[1].iov_base = (void *)rtlstats64; // caller-provided
 	iov[1].iov_len = sizeof(struct rtnl_link_stats64);
 	memset(&msg, 0, sizeof(msg));
@@ -116,9 +116,9 @@ fetch_stats64(struct rtnl_link_stats64 *rtlstats64, char const *ifname, int nlrt
 
 	if (nlresp.nlh.nlmsg_type == NLMSG_ERROR) {
 		// copy second iov into ans in first iov to get contiguous struct nlmsgerr
-		nlresp.ans.rtlstats64 = *rtlstats64;
-		assert(nlresp.err.nlerr.error < 0);
-		errno = -nlresp.err.nlerr.error;
+		nlresp.u.ans.rtlstats64 = *rtlstats64;
+		assert(nlresp.u.err.nlerr.error < 0);
+		errno = -nlresp.u.err.nlerr.error;
 		log_fatal("if-netmap-linux", "received NLMSG_ERROR: %d: %s", errno, strerror(errno));
 	}
 	if (nlresp.nlh.nlmsg_type != RTM_NEWSTATS) {

src/probe_modules/packet.c

@@ -10,6 +10,7 @@
 #include <stdio.h>
 #include <string.h>
 #include <assert.h>
+#include <time.h>
 
 #include "../../lib/includes.h"
 #include "../../lib/xalloc.h"

src/probe_modules/packet.h

@@ -159,7 +159,7 @@ static inline int check_dst_port(uint16_t port, int num_ports,
 	if (min <= max) {
 		return (to_validate <= max && to_validate >= min);
 	} else {
-		return (to_validate <= max ^ to_validate >= min);
+		return ((to_validate <= max) != (to_validate >= min));
 	}
 }
 

src/recv.c

@@ -100,7 +100,7 @@ void handle_packet(uint32_t buflen, const u_char *bytes,
 	// Here, we fake an ethernet frame (which is initialized to
 	// have ETH_P_IP proto and 00s for dest/src).
 	if (zconf.send_ip_pkts) {
-		const static uint32_t available_space = sizeof(fake_eth_hdr) - sizeof(struct ether_header);
+		static const uint32_t available_space = sizeof(fake_eth_hdr) - sizeof(struct ether_header);
 		assert(buflen > (uint32_t)zconf.data_link_size);
 		buflen -= zconf.data_link_size;
 		if (buflen > available_space) {