netstat -i: compute most field widths dynamically

The network and address fields were sometimes truncated for netstat -i
without -W, and often much too wide for netstat -i with the -W option.
Fields such as normal packet counts often overflowed.  As a result,
columns didn't line up, and large white spaces made it harder to
follow a line across the display.  Change the code to compute the
required field sizes for network, address, and various packet counts.
Hoist the code to format network and address into a subroutine that
can be called twice, once to measure the required field widths,
and once to emit the values.  Use separate field widths for input
and output packets, byte counts, and error and drop counters.
These are left at defaults (the preceding values) with the -h
option, in which case the fields have a limited total width.
An extra space is included between the Network and Address, which
otherwise seemed too close.

Change the mention of -W with -i in the man page to say that most
field widths are computed dynamically in this case.

Reviewed by:	sjg, glebius
Differential Revision:	https://reviews.freebsd.org/D41160

(cherry picked from commit 372e3d561d82aba7a66fcd4ecb49a4d0a9f69345)

2 files changed, 143 insertions, 77 deletions

diff --git a/usr.bin/netstat/if.c b/usr.bin/netstat/if.c
index 5ba4f3afc67b..e08a0462d56d 100644
--- a/usr.bin/netstat/if.c
+++ b/usr.bin/netstat/if.c
@@ -265,6 +265,99 @@ next_ifma(struct ifmaddrs *ifma, const char *name, const sa_family_t family)
 	return (ifma);
 }
 
+enum process_op { MEASURE, EMIT };
+
+static void
+process_ifa_addr(enum process_op op, struct ifaddrs *ifa, int *max_net_len,
+    int *max_addr_len, bool *network, bool *link)
+{
+	int net_len, addr_len;
+	const char *nn, *rn;
+
+	if (op == EMIT) {
+		net_len = *max_net_len;
+		addr_len = *max_addr_len;
+	}
+
+	switch (ifa->ifa_addr->sa_family) {
+	case AF_UNSPEC:
+		if (op == MEASURE) {
+			net_len = strlen("none");
+			addr_len = strlen("none");
+		} else {
+			xo_emit("{:network/%-*.*s}  ", net_len, net_len,
+			    "none");
+			xo_emit("{:address/%-*.*s} ", addr_len, addr_len,
+			    "none");
+		}
+		break;
+	case AF_INET:
+#ifdef INET6
+	case AF_INET6:
+#endif /* INET6 */
+		nn = netname(ifa->ifa_addr, ifa->ifa_netmask);
+		rn = routename(ifa->ifa_addr, numeric_addr);
+		if (op == MEASURE) {
+			net_len = strlen(nn);
+			addr_len = strlen(rn);
+		} else {
+			xo_emit("{t:network/%-*s}  ", net_len, nn);
+			xo_emit("{t:address/%-*s} ", addr_len, rn);
+		}
+
+		if (network != NULL)
+			*network = true;
+		break;
+	case AF_LINK:
+	    {
+		struct sockaddr_dl *sdl;
+		char linknum[sizeof("<Link#32767>")];
+
+		sdl = (struct sockaddr_dl *)ifa->ifa_addr;
+		snprintf(linknum, sizeof(linknum), "<Link#%d>", sdl->sdl_index);
+		if (op == MEASURE) {
+			net_len = strlen(linknum);
+			if (sdl->sdl_nlen == 0 &&
+			    sdl->sdl_alen == 0 &&
+			    sdl->sdl_slen == 0)
+				addr_len = 1;
+			else
+				addr_len = strlen(routename(ifa->ifa_addr, 1));
+		} else {
+			xo_emit("{t:network/%-*.*s}  ", net_len, net_len,
+			    linknum);
+			if (sdl->sdl_nlen == 0 &&
+			    sdl->sdl_alen == 0 &&
+			    sdl->sdl_slen == 0)
+				xo_emit("{P:/%*s} ", addr_len, "");
+			else
+				xo_emit("{t:address/%-*.*s} ", addr_len,
+				    addr_len, routename(ifa->ifa_addr, 1));
+		}
+		if (link != NULL)
+			*link = true;
+		break;
+	    }
+	}
+
+	if (op == MEASURE) {
+		if (net_len > *max_net_len)
+			*max_net_len = net_len;
+		if (addr_len > *max_addr_len)
+			*max_addr_len = addr_len;
+	}
+}
+
+static int
+max_num_len(int max_len, u_long num)
+{
+	int len = 2;		/* include space */
+
+	for (; num > 10; len++)
+		num /= 10;
+	return (MAX(max_len, len));
+}
+
 /*
  * Print a description of the network interfaces.
  */
@@ -274,7 +367,8 @@ intpr(void (*pfunc)(char *), int af)
 	struct ifaddrs *ifap, *ifa;
 	struct ifmaddrs *ifmap, *ifma;
 	u_int ifn_len_max = 5, ifn_len;
-	u_int has_ipv6 = 0, net_len = 13, addr_len = 17;
+	u_int net_len = strlen("Network "), addr_len = strlen("Address ");
+	u_int npkt_len = 8, nbyte_len = 10, nerr_len = 5;
 
 	if (interval)
 		return sidewaysintpr();
@@ -294,39 +388,51 @@ intpr(void (*pfunc)(char *), int af)
 		if ((ifa->ifa_flags & IFF_UP) == 0)
 			++ifn_len;
 		ifn_len_max = MAX(ifn_len_max, ifn_len);
-		if (ifa->ifa_addr->sa_family == AF_INET6)
-			has_ipv6 = 1;
-	}
-	if (Wflag) {
-		if (has_ipv6) {
-			net_len = 24;
-			addr_len = 39;
-		} else
-			net_len = 18;
+		process_ifa_addr(MEASURE, ifa, &net_len, &addr_len,
+		    NULL, NULL);
+
+#define	IFA_STAT(s)	(((struct if_data *)ifa->ifa_data)->ifi_ ## s)
+		if (!hflag) {
+			npkt_len = max_num_len(npkt_len, IFA_STAT(ipackets));
+			npkt_len = max_num_len(npkt_len, IFA_STAT(opackets));
+			nerr_len = max_num_len(nerr_len, IFA_STAT(ierrors));
+			nerr_len = max_num_len(nerr_len, IFA_STAT(iqdrops));
+			nerr_len = max_num_len(nerr_len, IFA_STAT(collisions));
+			if (dflag)
+				nerr_len = max_num_len(nerr_len,
+				    IFA_STAT(oqdrops));
+			if (bflag) {
+				nbyte_len = max_num_len(nbyte_len,
+				    IFA_STAT(ibytes));
+				nbyte_len = max_num_len(nbyte_len,
+				    IFA_STAT(obytes));
+			}
+		}
 	}
 
 	xo_open_list("interface");
 	if (!pfunc) {
 		xo_emit("{T:/%-*.*s}", ifn_len_max, ifn_len_max, "Name");
-		xo_emit(" {T:/%5.5s} {T:/%-*.*s} {T:/%-*.*s} {T:/%8.8s} "
-		    "{T:/%5.5s} {T:/%5.5s}",
+		xo_emit(" {T:/%5.5s} {T:/%-*.*s}  {T:/%-*.*s} {T:/%*.*s} "
+		    "{T:/%*.*s} {T:/%*.*s}",
 		    "Mtu", net_len, net_len, "Network", addr_len, addr_len,
-		    "Address", "Ipkts", "Ierrs", "Idrop");
+		    "Address", npkt_len, npkt_len, "Ipkts",
+		    nerr_len, nerr_len, "Ierrs", nerr_len, nerr_len, "Idrop");
 		if (bflag)
-			xo_emit(" {T:/%10.10s}","Ibytes");
-		xo_emit(" {T:/%8.8s} {T:/%5.5s}", "Opkts", "Oerrs");
+			xo_emit(" {T:/%*.*s}", nbyte_len, nbyte_len, "Ibytes");
+		xo_emit(" {T:/%*.*s} {T:/%*.*s}", npkt_len, npkt_len, "Opkts",
+		    nerr_len, nerr_len, "Oerrs");
 		if (bflag)
-			xo_emit(" {T:/%10.10s}","Obytes");
-		xo_emit(" {T:/%5s}", "Coll");
+			xo_emit(" {T:/%*.*s}", nbyte_len, nbyte_len, "Obytes");
+		xo_emit(" {T:/%*s}", nerr_len, "Coll");
 		if (dflag)
-			xo_emit(" {T:/%5.5s}", "Drop");
+			xo_emit(" {T:/%*.*s}", nerr_len, nerr_len, "Drop");
 		xo_emit("\n");
 	}
 
 	for (ifa = ifap; ifa; ifa = ifa->ifa_next) {
 		bool network = false, link = false;
 		char *name, *xname, buf[IFNAMSIZ+1];
-		const char *nn, *rn;
 
 		if (interface != NULL && strcmp(ifa->ifa_name, interface) != 0)
 			continue;
@@ -367,72 +473,29 @@ intpr(void (*pfunc)(char *), int af)
 		show_stat("lu", 6, "mtu", IFA_MTU(ifa), IFA_MTU(ifa), 0);
 #undef IFA_MTU
 
-		switch (ifa->ifa_addr->sa_family) {
-		case AF_UNSPEC:
-			xo_emit("{:network/%-*.*s} ", net_len, net_len,
-			    "none");
-			xo_emit("{:address/%-*.*s} ", addr_len, addr_len,
-			    "none");
-			break;
-		case AF_INET:
-#ifdef INET6
-		case AF_INET6:
-#endif /* INET6 */
-			nn = netname(ifa->ifa_addr, ifa->ifa_netmask);
-			rn = routename(ifa->ifa_addr, numeric_addr);
-			if (Wflag) {
-				xo_emit("{t:network/%-*s} ", net_len, nn);
-				xo_emit("{t:address/%-*s} ", addr_len, rn);
-			} else {
-				xo_emit("{d:network/%-*.*s}{et:network} ",
-				    net_len, net_len, nn, nn);
-				xo_emit("{d:address/%-*.*s}{et:address} ",
-				    addr_len, addr_len, rn, rn);
-			}
-
-			network = true;
-			break;
-		case AF_LINK:
-		    {
-			struct sockaddr_dl *sdl;
-			char linknum[sizeof("<Link#32767>")];
-
-			sdl = (struct sockaddr_dl *)ifa->ifa_addr;
-			snprintf(linknum, sizeof(linknum), "<Link#%d>", sdl->sdl_index);
-			xo_emit("{t:network/%-*.*s} ", net_len, net_len,
-			    linknum);
-			if (sdl->sdl_nlen == 0 &&
-			    sdl->sdl_alen == 0 &&
-			    sdl->sdl_slen == 0)
-				xo_emit("{P:/%*s} ", addr_len, "");
-			else
-				xo_emit("{t:address/%-*.*s} ", addr_len,
-				    addr_len, routename(ifa->ifa_addr, 1));
-			link = true;
-			break;
-		    }
-		}
+		process_ifa_addr(EMIT, ifa, &net_len, &addr_len,
+		    &network, &link);
 
-#define	IFA_STAT(s)	(((struct if_data *)ifa->ifa_data)->ifi_ ## s)
-		show_stat("lu", 8, "received-packets", IFA_STAT(ipackets),
-		    link|network, 1);
-		show_stat("lu", 5, "received-errors", IFA_STAT(ierrors),
+		show_stat("lu", npkt_len, "received-packets",
+		    IFA_STAT(ipackets), link|network, 1);
+		show_stat("lu", nerr_len, "received-errors", IFA_STAT(ierrors),
 		    link, 1);
-		show_stat("lu", 5, "dropped-packets", IFA_STAT(iqdrops),
+		show_stat("lu", nerr_len, "dropped-packets", IFA_STAT(iqdrops),
 		    link, 1);
 		if (bflag)
-			show_stat("lu", 10, "received-bytes", IFA_STAT(ibytes),
-			    link|network, 0);
-		show_stat("lu", 8, "sent-packets", IFA_STAT(opackets),
+			show_stat("lu", nbyte_len, "received-bytes",
+			    IFA_STAT(ibytes), link|network, 0);
+		show_stat("lu", npkt_len, "sent-packets", IFA_STAT(opackets),
 		    link|network, 1);
-		show_stat("lu", 5, "send-errors", IFA_STAT(oerrors), link, 1);
+		show_stat("lu", nerr_len, "send-errors", IFA_STAT(oerrors),
+		    link, 1);
 		if (bflag)
-			show_stat("lu", 10, "sent-bytes", IFA_STAT(obytes),
-			    link|network, 0);
-		show_stat("NRSlu", 5, "collisions", IFA_STAT(collisions),
+			show_stat("lu", nbyte_len, "sent-bytes",
+			    IFA_STAT(obytes), link|network, 0);
+		show_stat("NRSlu", nerr_len, "collisions", IFA_STAT(collisions),
 		    link, 1);
 		if (dflag)
-			show_stat("LSlu", 5, "dropped-packets",
+			show_stat("LSlu", nerr_len, "dropped-packets",
 			    IFA_STAT(oqdrops), link, 1);
 		xo_emit("\n");
 
diff --git a/usr.bin/netstat/netstat.1 b/usr.bin/netstat/netstat.1
index a675afa17f61..6c76a653d96c 100644
--- a/usr.bin/netstat/netstat.1
+++ b/usr.bin/netstat/netstat.1
@@ -317,6 +317,9 @@ See
 Avoid truncating addresses even if this causes some fields to overflow.
 See
 .Sx GENERAL OPTIONS .
+However, in most cases field widths are determined automatically with the
+.Fl i
+option, and this option has little effect.
 .It Fl f Ar protocol_family
 Filter by
 .Ar protocol_family .