netstat: various fixes.

Avoid fgets() into toybuf other than to skip header lines, preferring
fscanf() or xgetline() instead.

Remove the early returns if we fail to skip a header line (fixes #62).

Fix `netstat -xl` which was previously broken (because only -a would
include listening sockets).

Fix a variety of formatting issues, bringing the diff between toybox
netstat and net-tools netstat down (which was what I used for testing).

Use FLAG() more consistently.

1 files changed, 62 insertions, 81 deletions

diff --git a/toys/net/netstat.c b/toys/net/netstat.c
index 23cd9f6d..24a2ceed 100644
--- a/toys/net/netstat.c
+++ b/toys/net/netstat.c
@@ -36,40 +36,25 @@ GLOBALS(
   int wpad;
 )
 
-// convert address into text format.
 static void addr2str(int af, void *addr, unsigned port, char *buf, int len,
   char *proto)
 {
+  char pres[INET6_ADDRSTRLEN];
+  struct servent *se = 0;
   int pos, count;
-  struct servent *ser = 0;
 
-// TODO lib/net.c has ntop()
-  // Convert to numeric address
-  if (!inet_ntop(af, addr, buf, 256)) {
-    *buf = 0;
+  if (!inet_ntop(af, addr, pres, sizeof(pres))) perror_exit("inet_ntop");
 
-    return;
-  }
-  buf[len] = 0;
-  pos = strlen(buf);
-
-  // If there's no port number, it's a local :* binding, nothing to look up.
-  if (!port) {
-    if (len-pos<2) pos = len-2;
-    strcpy(buf+pos, ":*");
-
-    return;
-  }
-
-// TODO xgetaddrinfo()
-  if (!FLAG(n)) {
+  if (FLAG(n) || !port) {
+    strcpy(buf, pres);
+  } else {
     struct addrinfo hints, *result, *rp;
     char cut[4];
 
     memset(&hints, 0, sizeof(struct addrinfo));
     hints.ai_family = af;
 
-    if (!getaddrinfo(buf, NULL, &hints, &result)) {
+    if (!getaddrinfo(pres, NULL, &hints, &result)) {
       socklen_t sock_len = (af == AF_INET) ? sizeof(struct sockaddr_in)
         : sizeof(struct sockaddr_in6);
 
@@ -78,28 +63,31 @@ static void addr2str(int af, void *addr, unsigned port, char *buf, int len,
         if (!getnameinfo(rp->ai_addr, sock_len, buf, 256, 0, 0, 0)) break;
       freeaddrinfo(result);
       buf[len] = 0;
-      pos = strlen(buf);
     }
 
-    // Doesn't understand proto "tcp6", so truncate
+    // getservbyport() doesn't understand proto "tcp6", so truncate
     memcpy(cut, proto, 3);
     cut[3] = 0;
-    ser = getservbyport(htons(port), cut);
+    se = getservbyport(htons(port), cut);
   }
 
-  // Append :service
-  count = snprintf(0, 0, ":%u", port);
-  if (ser) {
-    count = snprintf(0, 0, ":%s", ser->s_name);
-    // sheer paranoia
+  if (!strcmp(buf, "::")) strcpy(buf, "[::]");
+
+  // Append :service or :* if port == 0.
+  if (se) {
+    count = snprintf(0, 0, ":%s", se->s_name);
+    // NI_MAXSERV == 32, which is greater than our minimum field width.
+    // (Although the longest service name on Debian in 2021 is only 16 bytes.)
     if (count>=len) {
       count = len-1;
-      ser->s_name[count] = 0;
+      se->s_name[count] = 0;
     }
-  }
+  } else count = port ? snprintf(0, 0, ":%u", port) : 2;
+  // We always show the port, even if that means clobbering the end of the host.
+  pos = strlen(buf);
   if (len-pos<count) pos = len-count;
-  if (ser) sprintf(buf+pos, ":%s", ser->s_name);
-  else sprintf(buf+pos, ":%u", port);
+  if (se) sprintf(buf+pos, ":%s", se->s_name);
+  else sprintf(buf+pos, port ? ":%u" : ":*", port);
 }
 
 // Display info for tcp/udp/raw
@@ -109,10 +97,10 @@ static void show_ip(char *fname)
   char *state_label[] = {"", "ESTABLISHED", "SYN_SENT", "SYN_RECV", "FIN_WAIT1",
                          "FIN_WAIT2", "TIME_WAIT", "CLOSE", "CLOSE_WAIT",
                          "LAST_ACK", "LISTEN", "CLOSING", "UNKNOWN"};
-  FILE *fp = fopen(fname, "r");
+  FILE *fp = xfopen(fname, "r");
 
-  if (!fp) return perror_msg("'%s'", fname);
-  if(!fgets(toybuf, sizeof(toybuf), fp)) return; //skip header.
+  // Skip header.
+  fgets(toybuf, sizeof(toybuf), fp);
 
   while (fgets(toybuf, sizeof(toybuf), fp)) {
     char lip[256], rip[256];
@@ -120,7 +108,7 @@ static void show_ip(char *fname)
       struct {unsigned u; unsigned char b[4];} i4;
       struct {struct {unsigned a, b, c, d;} u; unsigned char b[16];} i6;
     } laddr, raddr;
-    unsigned lport, rport, state, txq, rxq, num, uid, nitems;
+    unsigned lport, rport, state, txq, rxq, num, uid, af = AF_INET6;
     unsigned long inode;
 
     // Try ipv6, then try ipv4
@@ -131,19 +119,19 @@ static void show_ip(char *fname)
       &raddr.i6.u.c, &raddr.i6.u.d, &rport, &state, &txq, &rxq,
       &uid, &inode))
     {
-      nitems = AF_INET;
+      af = AF_INET;
       if (10 != sscanf(toybuf,
         " %d: %x:%x %x:%x %x %x:%x %*X:%*X %*X %d %*d %ld",
         &num, &laddr.i4.u, &lport, &raddr.i4.u, &rport, &state, &txq,
         &rxq, &uid, &inode)) continue;
-    } else nitems = AF_INET6;
+    }
 
     // Should we display this? (listening or all or TCP/UDP/RAW)
     if (!(FLAG(l) && (!rport && (state&0xA))) && !FLAG(a) && !(rport&0x70))
       continue;
 
-    addr2str(nitems, &laddr, lport, lip, TT.wpad, label);
-    addr2str(nitems, &raddr, rport, rip, TT.wpad, label);
+    addr2str(af, &laddr, lport, lip, TT.wpad, label);
+    addr2str(af, &raddr, rport, rip, TT.wpad, label);
 
     // Display data
     s = label;
@@ -177,46 +165,43 @@ static void show_unix_sockets(void)
 {
   char *types[] = {"","STREAM","DGRAM","RAW","RDM","SEQPACKET","DCCP","PACKET"},
        *states[] = {"","LISTENING","CONNECTING","CONNECTED","DISCONNECTING"},
-       *s, *ss;
+       *filename = 0;
   unsigned long refcount, flags, type, state, inode;
   FILE *fp = xfopen("/proc/net/unix", "r");
 
-  if(!fgets(toybuf, sizeof(toybuf), fp)) return; //skip header.
-
-  while (fgets(toybuf, sizeof(toybuf), fp)) {
-    unsigned offset = 0;
-
-    // count = 6 or 7 (first field ignored, sockets don't always have filenames)
-    if (6<sscanf(toybuf, "%*p: %lX %*X %lX %lX %lX %lu %n",
-      &refcount, &flags, &type, &state, &inode, &offset))
-        continue;
+  // Skip header.
+  fgets(toybuf, sizeof(toybuf), fp);
 
+  while (fscanf(fp, "%*p: %lX %*X %lX %lX %lX %lu%m[^\n]", &refcount, &flags,
+                &type, &state, &inode, &filename) >= 5) {
     // Linux exports only SO_ACCEPTCON since 2.3.15pre3 in 1999, but let's
     // filter in case they add more someday.
     flags &= 1<<16;
 
-    // Only show unconnected listening sockets with -a
-    if (state==1 && flags && !(toys.optflags&FLAG_a)) continue;
+    // Only show unconnected listening sockets with -a or -l.
+    if (state==1 && flags && !(FLAG(a) || FLAG(l))) continue;
 
     if (type==10) type = 7; // move SOCK_PACKET into line
     if (type>ARRAY_LEN(types)) type = 0;
     if (state>ARRAY_LEN(states) || (state==1 && !flags)) state = 0;
+
+    if (state!=1 && FLAG(l)) continue;
+
     sprintf(toybuf, "[ %s]", flags ? "ACC " : "");
-    printf("unix  %-6ld %-11s %-10s %-13s %8lu ",
+    printf("unix  %-6ld %-11s %-10s %-13s %-8lu ",
       refcount, toybuf, types[type], states[state], inode);
     if (FLAG(p)) {
       struct num_cache *nc = get_num_cache(TT.inodes, inode);
 
-      printf("%-19.19s", nc ? nc->data : "-");
+      printf("%-19.19s ", nc ? nc->data : "-");
     }
 
-    if (offset) {
-      if ((ss = strrchr(s = toybuf+offset, '\n'))) *ss = 0;
-      printf("%s", s);
-    }
-    xputc('\n');
+    if (filename) {
+      printf("%s\n", filename+!FLAG(p));
+      free(filename);
+      filename = 0;
+    } else xputc('\n');
   }
-
   fclose(fp);
 }
 
@@ -265,18 +250,16 @@ static void display_routes(void)
   char iface[64]={0};
   FILE *fp = xfopen("/proc/net/route", "r");
 
-  if(!fgets(toybuf, sizeof(toybuf), fp)) return; //skip header.
+  // Skip header.
+  fgets(toybuf, sizeof(toybuf), fp);
 
   printf("Kernel IP routing table\n"
           "Destination\tGateway \tGenmask \tFlags %s Iface\n",
-          !(toys.optflags&FLAG_e) ? "  MSS Window  irtt" : "Metric Ref    Use");
-
-  while (fgets(toybuf, sizeof(toybuf), fp)) {
-     char *destip = 0, *gateip = 0, *maskip = 0;
+          !FLAG(e) ? "  MSS Window  irtt" : "Metric Ref    Use");
 
-     if (11 != sscanf(toybuf, "%63s%x%x%X%d%d%d%x%d%d%d", iface, &dest,
-       &gate, &flags, &ref, &use, &metric, &mask, &mss, &win, &irtt))
-         break;
+  while (fscanf(fp, "%63s%x%x%X%d%d%d%x%d%d%d", iface, &dest, &gate, &flags,
+                &ref, &use, &metric, &mask, &mss, &win, &irtt) == 11) {
+    char *destip = 0, *gateip = 0, *maskip = 0;
 
     // skip down interfaces.
     if (!(flags & RTF_UP)) continue;
@@ -285,12 +268,12 @@ static void display_routes(void)
 
     if (dest) {
       if (inet_ntop(AF_INET, &dest, out, 16)) destip = out;
-    } else destip = (toys.optflags&FLAG_n) ? "0.0.0.0" : "default";
+    } else destip = FLAG(n) ? "0.0.0.0" : "default";
     out += 16;
 
     if (gate) {
       if (inet_ntop(AF_INET, &gate, out, 16)) gateip = out;
-    } else gateip = (toys.optflags&FLAG_n) ? "0.0.0.0" : "*";
+    } else gateip = FLAG(n) ? "0.0.0.0" : "*";
     out += 16;
 
 // TODO /24
@@ -311,27 +294,26 @@ static void display_routes(void)
     if (!FLAG(e)) printf("%5d %-5d %6d %s\n", mss, win, irtt, iface);
     else printf("%-6d %-2d %7d %s\n", metric, ref, use, iface);
   }
-
   fclose(fp);
 }
 
 void netstat_main(void)
 {
   int tuwx = FLAG_t|FLAG_u|FLAG_w|FLAG_x;
-  char *type = "w/o";
+  char *type = "w/o servers";
 
   TT.wpad = FLAG(W) ? 51 : 23;
   if (!(toys.optflags&(FLAG_r|tuwx))) toys.optflags |= tuwx;
   if (FLAG(r)) display_routes();
   if (!(toys.optflags&tuwx)) return;
 
-  if (FLAG(a)) type = "established and";
-  else if (FLAG(l)) type = "only";
+  if (FLAG(a)) type = "servers and established";
+  else if (FLAG(l)) type = "only servers";
 
   if (FLAG(p)) dirtree_read("/proc", scan_pids);
 
   if (toys.optflags&(FLAG_t|FLAG_u|FLAG_w)) {
-    printf("Active %s (%s servers)\n", "Internet connections", type);
+    printf("Active Internet connections (%s)\n", type);
     printf("Proto Recv-Q Send-Q %*s %*s State      ", -TT.wpad, "Local Address",
       -TT.wpad, "Foreign Address");
     if (FLAG(e)) printf(" User       Inode      ");
@@ -353,10 +335,9 @@ void netstat_main(void)
   }
 
   if (FLAG(x)) {
-    printf("Active %s (%s servers)\n", "UNIX domain sockets", type);
-
-    printf("Proto RefCnt Flags\t Type\t    State\t    %s Path\n",
-      FLAG(p) ? "PID/Program Name" : "I-Node");
+    printf("Active UNIX domain sockets (%s)\n", type);
+    printf("Proto RefCnt Flags       Type       State         I-Node%sPath\n",
+           FLAG(p) ? "   PID/Program Name     " : "   ");
     show_unix_sockets();
   }