[PATCH xtables v2] xtables-monitor: fix build with older glibc

[Baruch Siach <baruch@xxxxxxxxxx>]

glibc older than 2.19 only expose BSD style fields of struct tcphdr when
_BSD_SOURCE is define. Current glibc however, warn that _BSD_SOURCE is
deprecated. Migrate to the GNU style of tcphdr fields to make the code
compatible with any glibc version.

Fix the following build failure:

xtables-monitor.c: In function 'trace_print_packet':
xtables-monitor.c:406:43: error: 'const struct tcphdr' has no member named 'th_sport'
    printf("SPORT=%d DPORT=%d ", ntohs(tcph->th_sport), ntohs(tcph->th_dport));
                                           ^
xtables-monitor.c:406:66: error: 'const struct tcphdr' has no member named 'th_dport'
    printf("SPORT=%d DPORT=%d ", ntohs(tcph->th_sport), ntohs(tcph->th_dport));
                                                                  ^
...

Cc: Florian Westphal <fw@xxxxxxxxx>
Signed-off-by: Baruch Siach <baruch@xxxxxxxxxx>
---
v2: Use GNU tcphdr fields

Note: build tested only.
---
 iptables/xtables-monitor.c | 30 ++++++++++++++----------------
 1 file changed, 14 insertions(+), 16 deletions(-)

diff --git a/iptables/xtables-monitor.c b/iptables/xtables-monitor.c
index 3b1ca777a28a..5d1611122df5 100644
--- a/iptables/xtables-monitor.c
+++ b/iptables/xtables-monitor.c
@@ -403,26 +403,24 @@ static void trace_print_packet(const struct nftnl_trace *nlt, struct cb_arg *arg
 		case IPPROTO_UDP:
 			if (len < 4)
 				break;
-			printf("SPORT=%d DPORT=%d ", ntohs(tcph->th_sport), ntohs(tcph->th_dport));
+			printf("SPORT=%d DPORT=%d ", ntohs(tcph->source), ntohs(tcph->dest));
 			break;
 		case IPPROTO_TCP:
 			if (len < sizeof(*tcph))
 				break;
-			printf("SPORT=%d DPORT=%d ", ntohs(tcph->th_sport), ntohs(tcph->th_dport));
-			if (tcph->th_flags & (TH_FIN|TH_SYN|TH_RST|TH_PUSH|TH_ACK|TH_URG)) {
-				if (tcph->th_flags & TH_SYN)
-					printf("SYN ");
-				if (tcph->th_flags & TH_ACK)
-					printf("ACK ");
-				if (tcph->th_flags & TH_FIN)
-					printf("FIN ");
-				if (tcph->th_flags & TH_RST)
-					printf("RST ");
-				if (tcph->th_flags & TH_PUSH)
-					printf("PSH ");
-				if (tcph->th_flags & TH_URG)
-					printf("URG ");
-			}
+			printf("SPORT=%d DPORT=%d ", ntohs(tcph->source), ntohs(tcph->dest));
+			if (tcph->syn)
+				printf("SYN ");
+			if (tcph->ack)
+				printf("ACK ");
+			if (tcph->fin)
+				printf("FIN ");
+			if (tcph->rst)
+				printf("RST ");
+			if (tcph->psh)
+				printf("PSH ");
+			if (tcph->urg)
+				printf("URG ");
 			break;
 		default:
 			break;
-- 
2.19.1